packaging: move most packaging targets to own Makefile...
packaging: move most packaging targets to own Makefile
Since we're putting everything packaging under one roof, let's
define the make targets related to packaging there as well.
I didn't move the "osx" target because it is non-trivial.
Some targets did change slightly as part of the move. But it
was mostly around path normalization.
Differential Revision:
https://phab.mercurial-scm.org/D3552
