gas char/unsigned char casts

This patch removes many unneeded casts to char or unsigned char.  It's
worth noting that safe-ctype.h macros ISDIGIT and the like cope with
either signed or unsigned char.
In some cases a cast to unsigned char is replaced by anding with 0xff,
which accomplishes the same thing but doesn't rely on char being eight
bits.  The patch also removes pointer casts, and a few unsigned char
pointer variables.
22 files changed