Log Message:
libX11: update to 1.7.3.1.

This release of libX11 corrects a packaging problem in 1.7.3 which caused
the m4 files needed for autoreconf to not be included in the tarballs.

(ProTip: if you have an ACLOCAL variable set in your environment, and it
 doesn't have "-I m4" ahead of any other -I options, then automake may
 assume that any m4 files found via those other -I options don't need to
 be included in the tarballs when you run "make dist".)

As a bonus, this release also includes one tiny typo fix in the XIM specs.