fix PR9629 - We were lowering regexes like a{{b|c}}d into ab|cd, which

fix PR9629 - We were lowering regexes like a{{b|c}}d into ab|cd, which
is substantially different than a(b|c)d.  Form the latter regex instead.
This found a few problems in the testsuite, which serves as its test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129196 91177308-0d34-0410-b5e6-96231b3b80d8