[PATCH] Don't segfault in EmitCXXGlobalInitFunc when main file is a membuf

[Nico Weber]

Is it possible to test this?

I think if the input comes from stdin, sys::path::filename() returns <stdin>, which then gets turned into _stdin_ by the isPreprocessingNumberBody() loop – maybe this should be <null> / _null_ instead of the old _a spelling? (I don't care too much about this part.)

http://reviews.llvm.org/D5043