Add mtlib and lib targets

(Again, the libs aren't build with submakes yet)

Currently, the library dependencies don't work...

* New User works.
* External Editor routine was broken.  It would segfault due to incorrect
value for j being being passed in putuserrec.  Fixed.
* When changing the User Alias, it was not updating name.dat.  Fixed.
(Needs to be tested on a system that uses Real Names only,)
* A few typos and spelling errors in comments that are of no importance :)

DIRSEP, not SLASH

Reasoning for this is so you can have xpdev and xpdev-mt libraries in the
same location but have their respective object files separate.

Don't forget to add $(LIBPREFIX) to library filenames.

.path.c is now defined in build/Common.bmake
Continue to build library even if delete fails (file doesn't exist).

Fixed make directives (! must begin line for Borland make).
Added path.c/cpp paths.
Removed libobjs.mk (for now).