Fix CharByteWidth assertion in LiteralSupport.

Patch by Eelis van der Weegen.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190971 91177308-0d34-0410-b5e6-96231b3b80d8
Add specific warning flags for GNU ext in Sema.

This patch adds the following, more specific warning flags:

gnu-anonymous-struct
gnu-compound-literal-initializer
gnu-empty-struct
gnu-flexible-array-initializer
gnu-flexible-array-union-member
gnu-folding-constant
redeclared-class-member
gnu-redeclared-enum
gnu-union-cast
gnu-variable-sized-type-not-at-end

Patch by Peter Lewis.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190972 91177308-0d34-0410-b5e6-96231b3b80d8