Move stamp (dependency) files outside the (version specific) source
directories, so other packages can hardcode dependencies on them instead
of having to use <PACKAGE>_VERSION variables.
This is important as the variables in the make rules are evaluated when
the rules is seen, which might be before the dependent makefile is parsed
(and hence <PACKAGE>_VERSION variable is known, screwing up stuff.
The downside of this is that the package isn't automatically rebuilt
when the version changes (E.G. by a svn update) and you now also have to
remove the stamp files next to $(BUILD_DIR)/<PACKAGE>-* to force a rebuild.
The host versions shouldn't be visible in Kconfig, so remove the
reference to BR2_PACKAGE_PKGCONFIG everywhere and prefix the host targets
with host-.
At the same time add pkgconfig for the target (E.G. for development) and
let BR2_PACKAGE_PKGCONFIG control that package.
Notice: all defconfigs in the tree have been updated, but make sure to
disable the pkgconfig package (unless you want it) if you use an external
config, otherwise you'll end up with pkgconfig and glib2 in the target.
