massive rewrite of the pkgmaker logic

massive rewrite of the pkgmaker logic

When adjusting for auto-generated package/Config.in, I found out that
the splitting into Config.in{,.lib,.kmod} done by pkgmaker was rather
subversive to my approach. Categorisation of packages and subpackages
should be done via package section, which is enabled by this patch for
subpackages, too.

Instead of filling up the package subdirectories, use a common directory
package/pkgconfigs.d/ to contain all auto-generated Config.in files. In
order to allow simple assumption from config symbol to actual package
from within menuconfig (the path to the Config.in file containing the
current config symbol is printed as part of the help text), put all
generated Config.in files for a certain package into a common
subdirectory.

pkgmaker now saves each generated config symbol (excluding the flavours)
into it's own file, therefore allowing to sort subpackages of a package
into a different section.