Patch to check at compile time for overflow when
__builtin___memcpy_chk and similar builtins are
being used. Patch by Jacques Fortier (with added 
clang tests).  rdar://11076881


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218063 91177308-0d34-0410-b5e6-96231b3b80d8