[patch] add nan,qnan,snan rtl functions

[Doug Evans]

Hi.

fyi, I checked this in.

2010-01-20  Doug Evans  <dje@sebabeach.org>

	* rtx-funcs.scm (nan,qnan,snan): New rtl functions.
	* rtl-c.scm (nan,qnan,snan): New rtl functions.
	* doc/rtl.texi (Expressions): Add docs for them.