[nic] Allow the user to override the name the Makefile uses to refer to Theos.

From: Dustin L. Howett <dustin@howett.net>

git-svn-id: http://svn.howett.net/svn/theos/trunk@614 4410221e-0ddf-4ce3-99c0-2db6c0dbc727
[makefiles] Try to intuit the Makefile the user is using (make -f XXX), and use that for all sub-makes.

From: Dustin L. Howett <dustin@howett.net>

git-svn-id: http://svn.howett.net/svn/theos/trunk@615 4410221e-0ddf-4ce3-99c0-2db6c0dbc727