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

• PORT_LEN src/od-amiga/ami-rexx.c:70
• pot0dat src/od-amiga/amiga-kludges.h:94
• pot1dat src/od-amiga/amiga-kludges.h:95
• potgo src/od-amiga/amiga-kludges.h:96
• potinp src/od-amiga/amiga-kludges.h:97