Updates to tuklib_physmem and tuklib_cpucores.

Updates to tuklib_physmem and tuklib_cpucores.

Don't use #error to generate compile error, because some
compilers actually don't take it as an error. This fixes
tuklib_physmem on IRIX.

Fix incorrect error check for sysconf() return values.

Add AIX, HP-UX, and Tru64 specific code to detect the
amount RAM.

Add HP-UX specific code to detect the number of CPU cores.

Thanks a lot to Peter O'Gorman for initial patches,
testing, and debugging these fixes.