depends: fix native build
depends: give tarballs a default path
depends: add native zlib
depends: png-native depends on zlib-native
depends: rearrange so that we can add xbmc's internal depends in the future
depends: fix libiconv build
depends fixup gitignore after reorg
depends: add back missing Makefile
depends: disable ccache feature of swig

This rids us of the libz dependency