Refactor pkgconfig-jam generator
Refactor pkgconfig-jam generator

This patch is a structure change with no functional difference in the generated pkgconfig jamfile. Following this will be functional changes that have been made easier with this refactor.

vmrob/needy,bittorrent/needy,ccbrown/needy,vmrob/needy,bittorrent/needy,ccbrown/needy