Add support for stack map generation in the X86 backend.

Originally implemented by Lang Hames.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193811 91177308-0d34-0410-b5e6-96231b3b80d8
Add new calling convention for WebKit Java Script.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193812 91177308-0d34-0410-b5e6-96231b3b80d8