Adapt the MS-DOS build to the latest configury changes.
msdos/sed1v2.inp: In the recipe for $(leimdir)/leim-list.el, edit the
prerequisites to be "temacs$(EXEEXT) $(BOOTSTRAPEMACS)", to avoid
the need to rebuild $(bootstrap_exe), which requires a Unixy shell
via lisp/Makefile.in's "update-subdirs" command.
msdos/sedlibmk.inp (am_libgnu_a_OBJECTS): Adjust the removal of
careadlinkat.$(OBJEXT) to the changes in lib/Makefile.in.
msdos/sed2v2.inp (DATA_START, GC_SETJMP_WORKS, HAVE_MENUS)
(HAVE_MOUSE): Edit for DJGPP, according to what was previously
done on src/s/msdos.h.
msdos/gmalloc.c (GMALLOC_INHIBIT_VALLOC): Don't reference.
src/s/msdos.h (BSD_SYSTEM, DATA_START, GC_SETJMP_WORKS, HAVE_MOUSE)
(HAVE_MENUS): Don't define, defined by editing config.in with
msdos/sed2v2.inp.
(GMALLOC_INHIBIT_VALLOC): Don't define.
(MODE_LINE_BINARY_TEXT): Remove, not used anymore.