Add hacks for replacing some #defines in scripts

Note: A simpler approach would be replacing "#define GAME_FPS 60" and
the similar defines for GAME_FRAMETIME and CHAINGUN_FIRE_SKIPFRAMES
in the scripts with other values based on com_gameHz, for example to
"#define GAME_FPS 144".

However, that would have two disadvantages:
1. When changing com_gameHz, you'll have to reload the scripts
2. This changes the checksum of the scripts, so each time you change
   com_gameHz the checksum changes and your old savegames stop working.

Luckily the scripts already have functions (that are implemented in the
gamecode) that expose the FPS and FrameTime: sys.getTicksPerSecond()
 and sys.getFrameTime()

So now we modify the #defines to call those functions instead.
That will still break *old* savegames, but at least savegames made from
now on will still work no matter what you set com_gameHz to.

TODO: A problem with this approach is that the time sys.getFrameTime()
returns is scaled when in slow motion, so I'll probably have to add
another function for that

This code is partly based on code from Stradex' "Add com_gameHz to play
 with higher HZ/FPS" PR: dhewm#297

neo/idlib/Parser.cpp

@@ -1083,6 +1083,19 @@ int idParser::Directive_undef( void ) {
 	return true;
 }
 
+
+// DG: helperfunction for my hack in Directive_define()
+static idToken* createToken(const char* str, int type, int subtype, int line) {
+	idToken* ret = new idToken();
+	*ret = str;
+	ret->type = type;
+	ret->subtype = subtype;
+	ret->line = line;
+	ret->flags = 0;
+	ret->ClearTokenWhiteSpace();
+	return ret;
+}
+
 /*
 ================
 idParser::Directive_define
@@ -1126,6 +1139,90 @@ int idParser::Directive_define( void ) {
 	if ( !idParser::ReadLine( &token ) ) {
 		return true;
 	}
+
+	// Stradex/DG: Hack to support com_gameHZ (configurable framerate instead of fixed 60fps):
+	//    we replace GAME_FPS, GAME_FRAMETIME and CHAINGUN_FIRE_SKIPFRAMES #defines with script code
+	// NOTE: it's theoretically possible to just replace them with the current value instead
+	//   of function calls ("#define GAME_FPS 144"), but that changes the script's checksum
+	//   which makes loading savegames fail after changing com_gameHz
+	const char* defName = define->name;
+	int numHackTokens = 0;
+	idToken* hackTokens[12] = {};
+	if ( idStr::Icmp(defName, "GAME_FPS") == 0 || idStr::Icmp(defName, "GAME_FRAMETIME") == 0 ) {
+		// FIXME: in d3xp, getFrameTime returns gameLocal.msec, which is modified for slowmo, which is not what we want
+		const char* funName = (idStr::Icmp(defName, "GAME_FPS") == 0) ? "getTicsPerSecond" : "getFrameTime";
+		int line = token.line;
+
+		// change "#define GAME_FPS 60" to "#define GAME_FPS sys.getTicsPerSecond()"
+		// (or equivalent for GAME_FRAMETIME and sys.getFrameTime())
+		hackTokens[0] = createToken( "sys", TT_NAME, 3, line );
+		hackTokens[1] = createToken( ".", TT_PUNCTUATION, P_REF, line );
+		hackTokens[2] = createToken( funName, TT_NAME, strlen(funName), line ); // getTicsPerSecond or getFrameTime
+		hackTokens[3] = createToken( "(", TT_PUNCTUATION, P_PARENTHESESOPEN, line );
+		hackTokens[4] = createToken( ")", TT_PUNCTUATION, P_PARENTHESESCLOSE, line );
+		numHackTokens = 5;
+	}
+	else if ( idStr::Icmp(defName, "CHAINGUN_FIRE_SKIPFRAMES" ) == 0) {
+		int line = token.line;
+
+		// change "#define CHAINGUN_FIRE_SKIPFRAMES 7" (or similar) to
+		// "#define CHAINGUN_FIRE_SKIPFRAMES int( ( 0.118644 * sys.getTicsPerSecond() ) )
+		//   where 0.118644 is the value of "factor" below (sth like 7/59)
+		// Note: Yes, it looks like there's a superfluous set of parenthesis, but without them
+		//       it doesn't work. I guess that's a bug in the script compiler, but I have no
+		//       motivation to debug that further..
+
+		float origVal = ( token.type == TT_NUMBER ) ? token.GetFloatValue() : 7.0f;
+		// should divide by 60, but with 59 it rounds up a bit, esp. for 144 fps the resulting
+		// value is better (in the script we clamp to int and don't round): 7/60 * 144 = 16.8
+		// => converted to int that's 16, while 7/59 * 144 = 17.084 => 17 => closer to 16.8
+		// (and for other common values like 60 or 120 or 200 or 240 it doesn't make a difference)
+		// Note that clamping to int is important, so the following script code works as before:
+		//   "for( skip = 0; skip < CHAINGUN_FIRE_SKIPFRAMES; skip++ )"
+		// (if CHAINGUN_FIRE_SKIPFRAMES isn't 7 but 7.01, this runs 8 times instead of 7)
+		float factor = origVal / 59.0f;
+		char facStr[10];
+		idStr::snPrintf( facStr, sizeof(facStr), "%f", factor );
+
+		// int( ( 0.118644 * sys.getTicsPerSecond() ) )
+		hackTokens[0]  = createToken( "int", TT_NAME, 3, line );
+		hackTokens[1]  = createToken( "(", TT_PUNCTUATION, P_PARENTHESESOPEN, line );
+
+		hackTokens[2]  = createToken( "(", TT_PUNCTUATION, P_PARENTHESESOPEN, line );
+
+		hackTokens[3]  = createToken( facStr, TT_NUMBER, TT_DECIMAL | TT_FLOAT | TT_DOUBLE_PRECISION, line );
+		hackTokens[4]  = createToken( "*", TT_PUNCTUATION, P_MUL, line );
+		hackTokens[5]  = createToken( "sys", TT_NAME, 3, line );
+		hackTokens[6]  = createToken( ".", TT_PUNCTUATION, P_REF, line );
+		hackTokens[7]  = createToken( "getTicsPerSecond", TT_NAME, strlen("getTicsPerSecond"), line );
+		hackTokens[8]  = createToken( "(", TT_PUNCTUATION, P_PARENTHESESOPEN, line );
+		hackTokens[9]  = createToken( ")", TT_PUNCTUATION, P_PARENTHESESCLOSE, line );
+
+		hackTokens[10] = createToken( ")", TT_PUNCTUATION, P_PARENTHESESCLOSE, line );
+
+		hackTokens[11] = createToken( ")", TT_PUNCTUATION, P_PARENTHESESCLOSE, line );
+		numHackTokens = 12;
+	}
+
+	if ( numHackTokens != 0 ) {
+		// skip rest of the line, inject our hackTokens instead and return
+		while ( idParser::ReadLine( &token ) )
+		{};
+
+		define->tokens = hackTokens[0];
+		last = hackTokens[0];
+
+		for( int i=1; i < numHackTokens; ++i ) {
+			t = hackTokens[i];
+			last->next = t;
+			last = t;
+		}
+		last->next = NULL;
+
+		return true;
+	}
+	// DG: END of Hack.
+
 	// if it is a define with parameters
 	if ( token.WhiteSpaceBeforeToken() == 0 && token == "(" ) {
 		// read the define parameters