[fortran,patch] Extend IEEE support to all real kinds

[FX]

> FAIL: gfortran.dg/ieee/large_1.f90   -O0  (test for excess errors)
> Excess errors:
> large_1.f90:(.text+0x1792): undefined reference to `logbq’

Fixed by the patch there: https://gcc.gnu.org/ml/gcc-patches/2015-08/msg00124.html
Waiting for review.

FX