base.bbclass: Implement PACKAGECONFIG
These enabled options to be specified in the form:
PACKAGECONFIG ?? = "<default options>"
PACKAGECONFIG[foo] = "--enable-foo,--disable-foo,foo_depends,foo_runtime_depends"
So that DEPENDS, RDEPENDS_${PN} and EXTRA_OECONF can be automatically
built from specific options. Those options can easily be customised
by the distro config or the user.
Based on some ideas from Chris Elston <celston@katalix.com> but with
an improved easier to use one line interface.
(From OE-Core rev:
7a58911f6951abd56db9ebb37f8d6284d91fa514)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>