[fortran, patch] Handle POW/CPOW builtins for all floating-point types

[Tobias Burnus]

  FX wrote:
> I'll have to check... in your idea, would a real(kind=16) descriptor have only GFC_DTYPE_FLOAT128 set, or (GFC_DTYPE_FLOAT128 | GFC_DTYPE_REAL)?

Well, I think both will be the same: All 3 bits will be set to 1. You 
can only store 8 = 2^3 states in 3 bits, 7 states are currently in use ...

My idea was to use GFC_DTYPE_FLOAT128 for software REAL values. For 
backward compatibility, we still use GFC_DTYPE_REAL for REAL(10) and 
hardware REAL(16). All conditions in libgfortran have to use "==" as OR 
and AND will not work.

Tobias