extend.texi: Add ip2k port to description of attribute naked.

extend.texi: Add ip2k port to description of attribute naked.

	* doc/extend.texi: Add ip2k port to description of attribute
	naked.
	* doc/install.texi (Specific): Add ip2k description.
	* doc/install-old.texi (Configurations): Add ip2k to possible
	cpu types.
	* doc/md.texi: Document ip2k constraints.
	* config/ip2k/crt0.S: New file.
	* config/ip2k/ip2k-protos.h: New file.
	* config/ip2k/ip2k.c: New file.
	* config/ip2k/ip2k.h: New file.
	* config/ip2k/ip2k.md: New file.
	* config/ip2k/libgcc.S: New file.
	* config/ip2k/t-ip2k: New file.

Co-Authored-By: Alan Lehotsky <apl@alum.mit.edu>
Co-Authored-By: Bernd Schmidt <bernds@redhat.com>
Co-Authored-By: Dave Hudson <dave.hudson@ubicom.com>
Co-Authored-By: Frank Ch. Eigler <fche@redhat.com>
Co-Authored-By: Graham Stott <grahams@redhat.com>
Co-Authored-By: Jeff Johnston <jjohnstn@redhat.com>
Co-Authored-By: Matthew Green <mrg@redhat.com>
Co-Authored-By: Richard Henderson <rth@redhat.com>
From-SVN: r55122