One more small optimization: Where possible, for loops that do a search and...

One more small optimization:  Where possible, for loops that do a search and then try to break out of the loop early, eliminate the attempt to break out of the loop after the last search.  And with that, I'm declaring __dynamic_cast done.  Though if anyone sees any problems, has suggestions for improvements, or wants to contribute some test cases, that is certainly welcome feedback.

llvm-svn: 148246