* dwarf2read.c (lookup_dwo_unit): Return NULL if DWO not found.
	(init_cutu_and_read_dies): Flag a complaint, not error, for bad
	DWO stub.  If DWO isn't found, just use stub.
	(lookup_dwo_cutu): Don't try DWO if there's a DWP file.
* i686.din: New file.
* x86_64.din: New file.
* common.din: New file.
* cygwin.din: Delete.
* cygwin64.din: Delete.
* gendef: Rework to take options rather than using positional parameters.
Accept multiple files as input.
missing checkin
Sigh.  Another missing checkin.
* exceptions.cc (cygwin_exception::dumpstack): Guard against wild pointer
dereference.
(CYG_EXC_CONTINUE_EXECUTION): Define based on standard Windows definition.
(CYG_EXC_CONTINUE_SEARCH): Ditto.
(exception::handle): Move andreas detection earlier.  Make comment clearer.
(signal_exit): Set core-dumped flag.
* spawn.cc (system_call_cleanup): Rename from pthread_cleanup.  Extend
functionality.
(system_call_cleanup::system_call_cleanup): Set up signals like system()
requires.  Unblock previously-blocked signal handling.
(system_call_cleanup::~system_call_cleanup): Restore signal handling after
system().
(child_info_spawn::worker): Put signals on hold and use system_call_cleanup
class to set and restore signals rather than doing it prior to to running the
program.  Remove the ill-conceived pthread_cleanup stuff.
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