Making pkgconfig easier to use with autoconf

[Carl Worth]

(I didn't see a more relevant list for pkgconfig feature requests, so
please let me know if I missed something.)

First, I have to say I'm delighted with pkgconfig. It actually makes
doing some of the autotools-based build management almost bearable.

But, I am exceedingly lazy, and I'd like it to be one step
easier. Currently, in my configure.in, I have a list of package
dependencies, something like:

	PKG_CHECK_MODULES(CAIRO, slim >= 0.2.0 libic >= 0.1.3 xft xrender >= 0.6)

Then, I have a parallel list in my cairo.pc.in file:

	Requires: slim libic xft xrender

And I don't want to have to maintain both lists. Is there already a
way to do this, and I'm doing something wrong? Otherwise, how hard
would it be for the PKG_CHECK_MODULES macro to set a variable that I
could drop into my .pc.in file, something like:

	Requires: @PKG_CHECK_REQUIRES@

Thanks,

-Carl