Split -fsanitize=bounds to -fsanitize=array-bounds (for the frontend-inserted
check using the ubsan runtime) and -fsanitize=local-bounds (for the middle-end
check which inserts traps).

Remove -fsanitize=local-bounds from -fsanitize=undefined. It does not produce
useful diagnostics and has false positives (PR17635), and is not a good
compromise position between UBSan's checks and ASan's checks.

Map -fbounds-checking to -fsanitize=local-bounds to restore Clang's historical
behavior for that flag.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@193205 91177308-0d34-0410-b5e6-96231b3b80d8
Retain previous language linkage of friend function declarations

With this extension, friend function declarations will retain the language
linkage specified for previous declarations instead of emitting an error
diagnostic.

The feature is known to be compatible with GCC and MSVC and permits a
language to be specified indirectly where it cannot otherwise be written
directly in class scope.

Work is ongoing to improve linkage spec diagnostics.

Fixes PR17337.

Reviewed by Richard Smith.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@193206 91177308-0d34-0410-b5e6-96231b3b80d8