config: comment, minor upgrade, quote and layout configure.ac

config: comment, minor upgrade, quote and layout configure.ac

Group statements per section as per Autoconf standard layout
Quote statements where appropriate.
Autoconf recommends not using dnl instead of # for comments

Use AC_CONFIG_FILES to replace the deprecated AC_OUTPUT with parameters.
Add AC_CONFIG_SRCDIR([Makefile.am])
Update X.Org util-macros to version 1.8

This helps automated maintenance and release activities.
Details can be found in http://wiki.x.org/wiki/NewModuleGuidelines

Signed-off-by: Gaetan Nadon <memsize@videotron.ca>