Check for NULL link registers as found in initial stack frames when doing stack unwinding, instead of naively trying to check the instruction at that location. This fixes signal handling in threaded applications after recent changes regarding unwinding in libthr. While here, clean up our MD_FROB_UPDATE_CONTEXT() implementation a little.
Check for NULL link registers as found in initial stack frames when doing
stack unwinding, instead of naively trying to check the instruction at
that location. This fixes signal handling in threaded applications after
recent changes regarding unwinding in libthr. While here, clean up our
MD_FROB_UPDATE_CONTEXT() implementation a little.

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