Encoding mode used to be a compile time option, but now it's always
compiled in.

Also move the loading of profiles and input section activation in one
place. Leaving this in mp_initialize has the drawback that encoding
section profile will overwrite options set by the user in the command
line, since it's set after the CLI options are parsed and processed.
mp_parse_cfgfiles happens before parsing the CLI, so loading the profile
there is better.