Port to HP-UX ia64.

Also added fix for correclty building asimage in case not a single
external graphics support lib is found. In that case will build
the built-in versions of these libs (png, gif, jpg).


git-svn-id: http://root.cern.ch/svn/root/trunk@10428 27541ba8-7e3a-0410-8455-c3a389f83636