Add bitselect() builtin

Reviewed-By: Aaron Watry <awatry@gmail.com>

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@185836 91177308-0d34-0410-b5e6-96231b3b80d8
Implement barrier() builtin

Reviewed and Tested-by: Aaron Watry <awatry@gmail.com>

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@185837 91177308-0d34-0410-b5e6-96231b3b80d8
Add __CLC_ prefix to all macro definitions in headers

libclc was defining and undefing GENTYPE and several other macros with
common names in its header files.  This was preventing applications from
defining macros with identical names as command line arguments to the
compiler, because the definitions in the header files were masking the
macros defined as compiler arguements.

Reviewed-by: Aaron Watry <awatry@gmail.com>

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@185838 91177308-0d34-0410-b5e6-96231b3b80d8
Implement mad24() and mul24() builtins

Reviewed-by: Aaron Watry <awatry@gmail.com>

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@185839 91177308-0d34-0410-b5e6-96231b3b80d8