obstack: pacify HP C * lib/obstack.h (obstack_free) [!__GNUC__]: Rewrite to avoid warning "conversion from pointer to smaller integer" from HP C-ANSI-C - cc version B9007AA/B3910B A.06.26. It's safe to assume C89 or later nowadays, so cast to void instead of int. Privately reported by H.Merijn Brand. Also, change header to match glibc's, to make checking against glibc easier.

# See lib/git-merge-changelog.c for making this useful.
ChangeLog	merge=merge-changelog

# Run this to make 'git diff' on texinfo files give nicer hunk context:
#   git config diff.texinfo.funcname '^@node[	 ][	 ]*\\([^,][^,]*\\)'
*.texi* diff=texinfo