internals: Assume compiler supports a subset of ISO varargs syntax
We have considerable anecdotal evidence that every relevant compiler supports at least the small part of ISO varargs syntax that we need here, because tools/tool-common.h has contained
#define VERBOSE(...) do {} while (0)
since dbus 1.9.2 (2014) and nobody has complained yet. With that in mind, let's simplify.
Signed-off-by: Simon McVittie smcv@collabora.com