Add support for /Ob1 and -finline-hint-functions flags

Add support for /Ob1 (and equivalent -finline-hint-functions), which enable
inlining only for functions marked inline, either explicitly (via inline
keyword, for example), or implicitly (function definition in class body,
for example).

This works by enabling inlining pass, and adding noinline attribute to
every function not marked inline.

Patch by Rudy Pons <rudy.pons@ilod.org>!

Differential Revision: http://reviews.llvm.org/D20647

llvm-svn: 273440