[Bug preprocessor/63831] [5 Regression] r217292 causes segfaults with -MM

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63831

--- Comment #11 from Iain Sandoe <iains at gcc dot gnu.org> ---
unfortunaely, not quite (yet) complete.

I tried 217505 + c#10 - on x86_64-darwin12 all langs bootstrap proceeds up to
the build of Ada lib.

I reverted r217292 and re-tried - bootstrap passed, so still some gremlin
remains (i'll be glad to try to analyse, but no cycles until the weekend).

Also thanks for doing this work! 
Clang compatibility is a _very_ useful thing on Darwin.