Merge pull request #1 from jpopelka/master

Fix -nup in psnup.1 (patch from Fedora; thanks to Jiri Popelka for submitting it.)
README: Mention gnulib.
Add some autotools support for non-POSIX systems.
Remove a redundant declaration (from TeXLive patch-05-const)
Bump version to 1.21
Makefile.am: add LICENSE to EXTRA_DIST