doc change
fix doc
fixed `describe' bug and edit comments
	modified:   BUGS
	modified:   all-lisps.sh
        modified:   maxdoc/info-database.lisp
	modified:   mext_defmfun1/mext_defmfun1_code.lisp
Fix and improve mdefmvar
	modified:   defmfun1/maxdoc.lisp
	modified:   mext_defmfun1/mext_defmfun1_code.lisp
reorganize and document functions in mext_system. add
some files that were omitted from repo.
	new file:   build_essential.mac
	new file:   mext_defmfun1/README
	modified:   mext_defmfun1/mext_defmfun1.system
	modified:   mext_defmfun1/mext_defmfun1_code.lisp
	new file:   mext_defmfun1/rtests/rtest_mext_defmfun1.mac
	modified:   mext_system/mext-maxima-system.lisp
	modified:   mext_system/rtests/rtest_load_in_subdir.mac
	modified:   testall1.mac
edit doc.