Only run the jump-checker if there's a branch-protected scope *and* there's

a switch or goto somewhere in the function.  Indirect gotos trigger the
jump-checker regardless, because the conditions there are slightly more
elaborate and it's too marginal a case to be worth optimizing.

Turns off the jump-checker in a lot of cases in C++.  rdar://problem/7702918

llvm-svn: 109962