[gfortran] Add malloc and free intrinsics

[FX Coudert]

> I updated the documentation so that it mentions that Cray pointers are
> not yet supported, so that the example is not working yet; it says
> that the example is for 32-bit systems, and indicates that MALLOC/FREE
> are here to support legacy code, and hints that the Fortran 95
> intrinsics to do memory allocation are ALLOCATE/DEALLOCATE.
> 
> I changed the testsuite file so that it uses integer*8, that works on
> both 32- and 64-bit systems.

ping.

Built and tested on i686-linux. OK for mainline (apart from the doc typo 
noted by Brooks)?

FX

:ADDPATCH fortran: