Move llvm/Analysis/ObjCARCUtil.h to IR to fix layering.

This is included from IR files, and IR doesn't/can't depend on Analysis
(because Analysis depends on IR).

Also fix the implementation - don't use non-member static in headers, as
it leads to ODR violations, inaccurate "unused function" warnings, etc.
And fix the header protection macro name (we don't generally include
"LIB" in the names, so far as I can tell).