Verify scalar semantics in quantifier fast path

[natecook1000]

After #655 and #658 land, verify that indexes are handled correctly under scalar semantics in Processor._doQuantifyMatch and String.matchBitset. Also check on end/endIndex there and in _matchBuiltinCC.

[milseman]

Note that we currently don't perform the compiler optimizations to enable those specialized instructions in scalar-semantic mode. We should enable them and test them.