[PATCH] Avoid -ansi warnings for long long (part of #717)

[Havoc Pennington]

Hi,

Makes sense. Can you _-prefix it, _DBUS_GNUC_EXTENSION
(the other "consider it internal" things should have this too, but I 
think I decided it wasn't worth the risk of changing something in a 
public header, don't know)

Havoc