This patch adds the rank intrinsic of the TR 29113 draft. It is a bit 
boring until gfortran supports DIMENSION(..) ;-)

Build and regtested on x86-64-linux.
OK for the trunk?

Tobias

PS: The current draft of TR 29113 is available at 
http://j3-fortran.org/pipermail/interop-tr/2011-May/000710.html (version 
of Monday, 16 May)