Tweak the fix for PR3784: be less sensitive about just

how invokes are set up.  The fix could be disturbed by
register copies coming after the EH_LABEL, and also didn't
behave quite right when it was the invoke result that
was used in a phi node.  Also (see new testcase) fix
another phi elimination bug while there: register copies
in the landing pad need to come after the EH_LABEL, because
that's where execution branches to when unwinding.  If they
come before the EH_LABEL then they will never be executed...
Also tweak the original testcase so it doesn't use a no-longer
existing counter.
The accumulated phi elimination changes fix two of seven Ada
testsuite failures that turned up after landing pad critical
edge splitting was turned off.  So there's probably more to come.

llvm-svn: 67049