Separate a few reusable components from XZ Utils specific
code. The reusable code is now in "tuklib" modules. A few
more could be separated still, e.g. bswap.h.

Fix some bugs in lzmainfo.

Fix physmem and cpucores code on OS/2. Thanks to Elbert Pol
for help.

Add OpenVMS support into physmem. Add a few #ifdefs to ease
building XZ Utils on OpenVMS. Thanks to Jouk Jansen for the
original patch.