This patch is for PR101317, one of the bugs uncovered by the TS29113 
testsuite.  Here I'd observed that CFI_establish, etc was not diagnosing 
some invalid-argument situations documented in the standard, although it 
was properly catching others.  After fixing those I discovered a couple 
small mistakes in the test cases and fixed those too.

The testsuite fixes can either be committed with this patch or rolled 
into the TS29113 testsuite, depending on the order in which things are 
approved/committed.

OK?

-Sandra