* doc/autoconf.texi: Minor style cleanup.

* doc/autoconf.texi: Minor style cleanup.
Be consistent about spaces after commas.
Insert [] where empty args look a bit funny.
Fix some "i.e." and "e.g." usages.
Try to avoid "X/Y" usages.
Don't be pedantic about "ISO C99"; just say C99.
Prefer GNU style for spaces in front of parens.
(Function Portability): Comment about C89 versus C99
signed integer division.
(Particular Headers): Use current gnulib style for dirent
includes.