Allow passing extra CPPFLAGS.
Allow passing extra CPPFLAGS.

paulproteus/livegrep,paulproteus/livegrep,lekkas/livegrep,paulproteus/livegrep,wfxiang08/livegrep,lekkas/livegrep,lekkas/livegrep,wfxiang08/livegrep,wfxiang08/livegrep,lekkas/livegrep,paulproteus/livegrep,lekkas/livegrep,lekkas/livegrep,wfxiang08/livegrep,wfxiang08/livegrep,paulproteus/livegrep,paulproteus/livegrep,wfxiang08/livegrep