Bug fix for PR23577 (https://llvm.org/bugs/show_bug.cgi?id=23577#c0).
"1-4" specifiers are returned as numeric constants, not identifiers,
and should be treated as such. Currently pragma handler incorrectly
assumes that they are returned as identifiers.

Patch by Andrey Bokhanko.

Differential Revision: http://reviews.llvm.org/D9856