Fix ScriptVariant_t::Free()

Type FIELD_HSCRIPT is removed, it never sets SV_FREE.

strdup()ed strings are not free'd via free() instead of delete, which
would be the conformant way in standard C++. It matters not in Source,
since both use the same global allocator of the engine, but it is
tidier.

Add a comment why we feel fine deleting QAngle as Vector.

sp/src/public/vscript/ivscript.h

@@ -431,7 +431,28 @@ struct ScriptVariant_t
 	void operator=( QAngle &&vec )		{ m_type = FIELD_VECTOR; m_pAngle = new QAngle( vec ); m_flags |= SV_FREE; }
 #endif
 
-	void Free()								{ if ( ( m_flags & SV_FREE ) && ( m_type == FIELD_HSCRIPT || m_type == FIELD_VECTOR || m_type == FIELD_CSTRING ) ) delete m_pszString; } // Generally only needed for return results
+	void Free()
+	{
+		// Generally only needed for return results
+		if ( ! ( m_flags & SV_FREE ) )
+		{
+			return;
+		}
+
+		switch ( m_type )
+		{
+			case FIELD_VECTOR:
+				// QAngle and Vector share the type FIELD_VECTOR
+				// both are trivial to desctruct, so it should be fine to delete QAngle as Vector (or vice versa)
+				delete m_pVector;
+				return;
+			case FIELD_CSTRING:
+				free( (char*)m_pszString );
+				return;
+		}
+
+		AssertMsg( 0, "Don't know how to free script variant of type %d", m_type );
+	}
 
 	template <typename T>
 	T Get()