tmp: backup-and-move top-level Makefile

tmp: backup-and-move top-level Makefile

This is just a trick to facilitate the resolution of conflicts in
the upcoming merge of the master branch, where the to-level Makefile
has been broken up in several per-subdir makefiles fragments (that
are then included by the top-level one, thus keeping the build system
non-recursive).

* Makefile.sav: New, verbatim copy of the "old" Makefile.am.
* Makefile.am: Make it a symlink to Makefile.sav.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>