llvm-gcc 4.2 and gfortran

Hello, Everyone.

As of r41125 gfortran builds fine within llvm-gcc 4.2. So, volunteers
who know fortran well are needed to check it.

Bugfixes and bugreports are welcome.

PS: I expect stuff to be horrible broken, but who knows
PPS: long doubles (80 bit) are known not to be working.