[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
diff --git a/clang/docs/Modules.rst b/clang/docs/Modules.rst
index 4187654..e11145e 100644
--- a/clang/docs/Modules.rst
+++ b/clang/docs/Modules.rst
@@ -413,6 +413,9 @@
 cplusplus11
   C++11 support is available.
 
+gnuinlineasm
+  GNU inline ASM is available.
+
 objc
   Objective-C support is available.