Implement [dcl.align]p5 and C11 6.7.5/4: alignas cannot underalign.
Also support alignas(0), which C++11 and C11 require us to ignore.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174157 91177308-0d34-0410-b5e6-96231b3b80d8
Add a new -Wundefined-inline warning for inline functions which are used but not
defined. Fixes PR14993!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174158 91177308-0d34-0410-b5e6-96231b3b80d8
Fix diagnostic for bad alignas use: it can't be applied to functions.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174160 91177308-0d34-0410-b5e6-96231b3b80d8