R600: Set the noduplicate attribute on barrier() intrinsics

This will prevent LLVM optimization passes from creating illegal uses
of the barrier() intrinsic (e.g. calling barrier() from a conditional
that is not executed by all threads).

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@193753 91177308-0d34-0410-b5e6-96231b3b80d8
s/_CLC_DECL/_CLC_DEF/

Some function definitions were using _CLC_DECL, which meant that they
weren't being marked as always_inline.

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

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@193754 91177308-0d34-0410-b5e6-96231b3b80d8