R600: Mostly remove remaining AMDIL intrinsics.

Delete all unused ones, and add new AMDGPU named intrinsics for
the ones that are. Handle the old AMDIL names for comptability (although
remove their GCCBuiltin names) and add tests since there weren't any
for these before.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210827 91177308-0d34-0410-b5e6-96231b3b80d8