Support and generate Compare and Traps like CRT, CIT, etc.
Support Trap as legal DAG opcodes and generate "j .+2" for them by default.
Add support for Conditional Traps and use the If Converter to convert them into
the corresponding compare and trap opcodes.
Differential Revision: http://reviews.llvm.org/D21155
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272419 91177308-0d34-0410-b5e6-96231b3b80d8