[ccan] Valgrind + tests

[Tim Post]

Hi,

I was looking at TAP as well as wiki entries discussing running tests
under valgrind. valgrind/valgrind.h provides a very useful macro,
RUNNING_ON_VALGRIND which if > 0 provides the valgrind instance.

This means, modules can be a bit more specific when complaining to
stderr if running under valgrind, at least conveying the valgrind
instance.

What comes to mind is modifying tap to see if HAVE_VALGRIND_VALGRIND_H
is high, and printing the resulting instance in messages.

If this was defined in config.h, it would allow modules to be more
verbose if running under valgrind, turn asserts back on, etc,  of course
only if HAVE_VALGRIND is defined.

So, how welcome are changes to config.h?

Cheers,
--Tim