Tweaked Makefile.in so that post-configured Makefile tests for a Cygwin build

Tweaked Makefile.in so that post-configured Makefile tests for a Cygwin build
environment, and if detected, explicitly adjusts the link order so that
libcygwin links *before* libiberty.a.  This gets around a Cygwin problem with
getopt()'s optind/optarg symbols.  See, for example:

http://sources.redhat.com/ml/cygwin/2004-04/msg01179.html

Also tweaked cygwin-elf.h and elf2flt.c so that Cygwin builds for MicroBlaze
target work as expected.

Patch sumbitted by John Williams <jwilliams@itee.uq.edu.au>