[binutils-gdb] Fix amd64 windows unwinding issues within MS dlls.

[sergiodj+buildbot@redhat.com]

*** TEST RESULTS FOR COMMIT 670f82d437c21ec9c8f59a365336163e0381149d ***

Author: Tristan Gingold <gingold@adacore.com>
Branch: master
Commit: 670f82d437c21ec9c8f59a365336163e0381149d

Fix amd64 windows unwinding issues within MS dlls.
Unwind info in system dlls uses almost all possible codes, contrary to unwind
info generated by gcc.  A few issues have been discovered: incorrect handling
of SAVE_NONVOL opcodes and incorrect in prologue range checks.  Furthermore I
added comments not to forget what has been investigated.

gdb/ChangeLog:
	* amd64-windows-tdep.c (amd64_windows_find_unwind_info): Move
	redirection code to ...
	(amd64_windows_frame_decode_insns): ... Here.  Fix in prologue
	checks.  Fix SAVE_NONVOL operations.  Add debug code and comments.