[Modules] Add 'gnuinlineasm' to the 'requires-declaration' feature-list.

This adds support for modules that require (no-)gnu-inline-asm
environment, such as the compiler builtin cpuid submodule.

This is the gnu-inline-asm variant of https://reviews.llvm.org/D23871

Differential Revision: https://reviews.llvm.org/D23905

rdar://problem/26931199

llvm-svn: 280159