Always print Timidity as supported decoder if built

[ericoporto]

When Timidity is included with the build, it should always print

Supported sound decoders:
- MIDI decoder, using a subset of TiMidity : MIDI,MID,

Currently if either the timidity.cfg is not found or it has something wrong in it or in the pointed soundfont, then this line doesn't show up. But this line is the best diagnostic we have that SDL2_Sound was indeed built with Timidity support.

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Not needed, but this would be perfect (I want a pony):

• in release config, when loading timidity.cfg it should log information about all steps in an internal buffer, and once an attempt is made to read a Midi file for the first time, if timidity was not correctly initialized, it should print to the log the previous accumulated internal log buffer lines and then this buffer should be emptied. (without Reading timidity soundfont from SDL_rwops #69, we don't own the logic to finding things and it's hard to debug what's going on when it's on someone's else machine)