gcc 6 with -Wall -Wextra warns:
code/botlib/l_precomp.c: In function ‘PC_NameHash’:
code/botlib/l_precomp.c:551:2: warning: ‘register’ is not at beginning of declaration [-Wold-style-declaration]
int register hash, i;
^~~
Modern compilers either ignore the register storage class when
generating code, or generate better code without it, so just remove
most of them.
The remaining uses are in third-party bundled libraries (libjpeg, zlib),
and in a PowerPC-specific inline function consisting of inline
assembler (because I'm not 100% confident that it doesn't have
some practical use there).