Defines starting with `u' in src/od-amiga

• UAEIFF src/od-amiga/ami-win.c:194
• UAE_PORTNAME src/od-amiga/ami-rexx.c:68
• UAESM src/od-amiga/ami-win.c:195
• USE_AHIDEVICE src/od-amiga/sound.h:10
• USE_CYBERGFX src/od-amiga/ami-win.c:54
• use_dither src/od-amiga/ami-win.c:191
• use_gray src/od-amiga/ami-win.c:192