autoconf: Scrape the version from configs/default

Added the make script version.mk to print the various version numbers
from configs/default. This is used to substitute the version in autoconf
rather than duplicating it in both places.

docs/devinfo.html

@@ -136,11 +136,11 @@ Update the docs/VERSIONS file too.
 
 <p>
 Edit the MESA_MAJOR, MESA_MINOR and MESA_TINY version numbers in
-configs/default and configure.ac.
+configs/default.
 </p>
 
 <p>
-Make sure the values in src/mesa/main/version.h is correct.
+Make sure the values in src/mesa/main/version.h are correct.
 </p>
 
 <p>