Improve pkg-config's configure instructure and bring it bang

Improve pkg-config's configure instructure and bring it bang
Author: keybuk
Date: 2004-06-07 23:43:21 GMT
Improve pkg-config's configure instructure and bring it bang
up to date.

* pkg.m4: Complete rewrite.
(PKG_PROG_PKG_CONFIG): if PKG_CONFIG not defined, find the
pkg-config in the path or $host-pkg-config if cross-compiling,
check that is of at least version 0.9.0 or one given.
(_PKG_CONFIG): internal macro to call pkg-config.
(PKG_CHECK_MODULES): same semantics as the previous incarnation
except you can prevent pkg-config from being called by defining
xxx_CFLAGS and xxx_LIBS yourself, additionally all results are
cached.
* README, pkg-config.1: Adjust documentation to match.