on amd64 (and likely other 64-bit architectures):
- Prototype for `void *qwglGetProcAddress(char *symbol)' was guarded by
#ifdef __linux__; this was not a problem on i386, where sizeof(void *)
/actual return type/ == sizeof(int) /assumed return type of undeclared
function/. On amd64, returned pointer would sometimes get truncated,
leading to a program's crash. Mend this by turning `#ifdef __linux__'
condition essentially into `#ifndef _WIN32'
- Software renderer was typedef'ing PIXEL24 as `unsigned long'; fix it
by using `unsigned int' type instead
- Remove `-s' from OPTIMIZED_CFLAGS: stripping is taken care of during
installation (subject to WITH_DEBUG); also remove optimization flag
`-fexpensive-optimizations' as it is not being supported by Clang
- While here, fix `version' console command to report correct operating
system and architecture names
- Employ options helper target to install documentation; add more useful
changelogs and drop `quake2.3dfxgl' file (meaningless these days)
01726beb98