Default ./configure paths

Hello, while packaging XEmacs 21.4.4 I ran into some difficulties because: 1. datadir and libdir do not work like described in the documentation: I am running ./configure with `--datadir=/usr/share --libdir=/usr/lib'. INSTALL indicates that the directories | /usr/lib/xemacs-21.4.4/<architecture> | /usr/share/xemacs-21.4.4/lisp | /usr/share/xemacs-21.4.4/etc will be created. Indeed the <architecture> dir will be created under the datadir | /usr/share/xemacs-21.4.4/<architecture> This means the --libdir behavior or the INSTALL-file is wrong 2. mandir is being set in an unusual manner: The FHS requires to put man-pages under /usr/share/man. Therefore I have to change the mandir variable under Linux. XEmacs defines it in the Makefile.in.in as | mandir=＠mandir＠ | manext=.1 and in configure.in as | mandir='${prefix}/man/man1' This is redundantly (when moving pages from section 1 to section x, both manext and mandir must be changed) and unusually for GNU/Linux[1] Although it is not absolutely necessarily to fix this, I have attached a patch changing the mandir-behavior. 3. Common ./configure scripts understand more options: ./configure scripts following the GNU/Linux standard understand options like --sbindir, --libexecdir, --sysconfdir... Supporting these options (without an action behind) makes it more easy to build XEmacs with general rules. Current XEmacs fails to build with them. Enrico Footnotes: [1] see standards.info/Directory Variables. There mandir is suggested to be ${prefix}/man without the trailing manext.