Fix build on OpenIndiana

Fix build on OpenIndiana

"Fix" is probably too strong a word here, it wasn't really broken in the
first place.  Just a tiny tweak to autogen.sh was the only "fix" needed
here.

This changeset also documents (in PROBLEMS) the missing deps needed to
build SXEmacs on OpenIndiana.

	* autogen.sh: Only add the xpg4/bin directory to the $PATH if this
	isn't OpenIndiana.

	* PROBLEMS: Document build quirks for OpenIndiana.

Signed-off-by: Steve Youngs <steve@sxemacs.org>