we do not save anything by limiting a variable to an unsigned char,
since the compiler aligns it at machine word size anyway.  however by
using the full machine word, we save one instruction, and we remove
the useless artificial limitation to 255.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7203 09075e82-0dd4-0310-85a5-a0d7c8717e4f