File names mangled for MS-DOS

[Eric Cushman Hill <eric>]

This is a first cut at the file name mangling to make names fit
into MS-DOS.  Markm and I just came up with this.  We invite
improvements.

Old Name		New Name
.h			c.h
.c			c.c
.o			c.o
-pvt.hxx		p.hxx
-sto.o			w.o
-stb.cxx		s.cxx
-stb.o			s.o
-pvt-stb.cxx		q.cxx
-pvt-stb.o		q.o
.hxx			c.hxx
.cxx			x.cxx
.o			x.o
-test.cxx		t.cxx
-test.o			t.o
.test			t.exe
.ref			r.txt
.out			o.txt
.diffs			d.txt