Get rid of compiler warnings

[CeRiAl]

Improve code to get rid of compiler warnings.

[CeRiAl]

Added commits:
4d3217f
c5e6299
4b5cc17
70ef5e1
6b497ab
e10b2a3
9cc93f4

These fix most of the warnings.

Still we have these:

/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp: In member function ‘uint32 XMidi::convertListToMTrk(unsigned char*, const XMidi::midi_event*)’:
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp:516:9: warning: variable ‘i_start’ set but not used [-Wunused-but-set-variable]
     int i_start;
         ^~~~~~~
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp: In static member function ‘static bool XMidi::handleChunkXMID(XMidi::XMidiFile*, const unsigned char*, uint32)’:
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp:728:7: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation]
     } else
       ^~~~
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp:737:9: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘else’
         if (!result) {
         ^~

and

/home/runner/work/freesynd/freesynd/src/system_sdl.cpp: In member function ‘virtual bool SystemSDL::pumpEvents(FS_Event*)’:
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:292:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_RSHIFT;
                                                    ^~~~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:298:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_RCTRL;
                                                    ^~~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:301:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_LCTRL;
                                                    ^~~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:304:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_RALT;
                                                    ^~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:307:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_LALT;
                                                    ^~~~~~~~

[CeRiAl]

Added commits:
8d56e39
fb2d32a

These commits fix these warnings:

/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp: In member function ‘uint32 XMidi::convertListToMTrk(unsigned char*, const XMidi::midi_event*)’:
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp:516:9: warning: variable ‘i_start’ set but not used [-Wunused-but-set-variable]
     int i_start;
         ^~~~~~~
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp: In static member function ‘static bool XMidi::handleChunkXMID(XMidi::XMidiFile*, const unsigned char*, uint32)’:
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp:728:7: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation]
     } else
       ^~~~
/home/runner/work/freesynd/freesynd/src/sound/xmidi.cpp:737:9: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘else’
         if (!result) {
         ^~

Still, we have these few left:

/home/runner/work/freesynd/freesynd/src/system_sdl.cpp: In member function ‘virtual bool SystemSDL::pumpEvents(FS_Event*)’:
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:292:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_RSHIFT;
                                                    ^~~~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:298:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_RCTRL;
                                                    ^~~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:301:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_LCTRL;
                                                    ^~~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:304:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_RALT;
                                                    ^~~~~~~~
/home/runner/work/freesynd/freesynd/src/system_sdl.cpp:307:52: warning: enum constant in boolean context [-Wint-in-bool-context]
                     keyModState_ = keyModState_ & !KMD_LALT;
                                                    ^~~~~~~~

[misutoneko]

The remaining warnings can be eliminated by adding parenthesis, like so:

keyModState_ = keyModState_ & !(KMD_RSHIFT);