Windows support dropped from gcc trunk

[Tim Prince]

Since Sept. 26, the partial support for Windows 64-bit has been dropped
from gcc trunk:
winnt.c apparently has problems with seh, which prevent bootstrapping,
and prevent the new gcc from building libraries.
libgfortran build throws a fatal error on account of lack of support for
__float128, even if a working gcc is used.
I didn't see any notification about this; maybe it wasn't a concensus
decision?
There are satisfactory pre-built gfortran 5.2 compilers (including
libgomp, although that is off by default and the testsuite wants acc as
well as OpenMP) available in cygwin64 (test version) and (apparently)
mingw-64.

-- 
Tim Prince