fix semaphore access (it's a struct, not a pointer)
make handle_input_event non-static, it's used from xwin.c

gfx-x11/libgfxdep.a(xwin.o): In function `handle_hotkey_event':
/media/3T/git-mirror/PUAE/src/gfx-x11/../../src/include/hotkeys.h:40:
 undefined reference to `handle_input_event'
collect2: error: ld returned 1 exit status
xwin.c: fix segfault (all params are 0)
gtk: fix uninitialized semaphore and resulting crash