Update to 2.6.3.
* Add a generic check for deprecated macros (e.g. the recent autotools batch),
and add USE_MESA to the set 
* Only use USE_LIBTOOL_VER for checking .la file installation 
* Add a check for USE_LIBLTDL and warn about directly using a libltdl
* Check distinfo to make sure each file in DISTFILES has SIZE and MD5 entries
if NO_SIZE and NO_CHECKSUM are not defined
Submitted by: krion and tobez