Work around an annoying, non-standard optimization in the glibc

headers, where malloc (and many other libc functions) are declared
with empty throw specifications, e.g.,  

  extern void *malloc (__SIZE_TYPE__ __size) throw () __attribute__
  ((__malloc__)) ;

The C++ standard doesn't seem to allow this, and redeclaring malloc as
the standard permits (as follows) resulted in Clang (rightfully!)
complaining about mis-matched exception specifications.

  void *malloc(size_t size);

We work around this by silently propagating an empty throw
specification "throw()" from a function with C linkage declared in a
system header to a redeclaration that has no throw specifier.

Ick.

llvm-svn: 95969