[analyzer] Use a smarter algorithm to find the last block in an inlined call.

[analyzer] Use a smarter algorithm to find the last block in an inlined call.

Previously we would search for the last statement, then back up to the
entrance of the block that contained that statement. Now, while we're
scanning for the statement, we just keep track of which blocks are being
exited (in reverse order).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169526 91177308-0d34-0410-b5e6-96231b3b80d8