Fix the MSDOS build as fallout from the latest Makefile.in changes.

Fix the MSDOS build as fallout from the latest Makefile.in changes.

 config.bat <lib-src>: Edit out lines that begin with several #
 characters.

 msdos/sedlisp.inp (VPATH): Don't edit, no longer needed.
 (lisp, srcdir): Adapt to lisp/Makefile.in changes.
 (abs_top_builddir): New edit.
 msdos/sed3v2.inp (KRB4LIB, DESLIB, KRB5LIB, CRYPTOLIB, COM_ERRLIB)
 (LIBHESIOD, LIBRESOLV, LIBS_MAIL): Edit to empty values.
 msdos/sed3.inp (KRB4LIB, DESLIB, KRB5LIB, CRYPTOLIB, COM_ERRLIB)
 (LIBHESIOD, LIBRESOLV, LIBS_MAIL): Edit to empty values.
 msdos/sed1v2.inp (abs_builddir): Edit into "../src".