-fcatch-undefined-behavior: Factor emission of the creation of, and branch to,

-fcatch-undefined-behavior: Factor emission of the creation of, and branch to,
the trap BB out of the individual checks and into a common function, to prepare
for making this code call into a runtime library. Rename the existing EmitCheck
to EmitTypeCheck to clarify it and to move it out of the way of the new
EmitCheck.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@163451 91177308-0d34-0410-b5e6-96231b3b80d8