Fix a typo and add a missing .El.
Add an xref to dtrace-ip(4).
Merge branch 'master' into 20131006-dtrace-mdoc

Conflicts:
	cddl/contrib/opensolaris/cmd/dtrace/dtrace.1
Man page for the udp provider.
Sentences start on new lines.
Xrefs, and add DTrace options in the example.
Install dtrace-udp.4.
Merge branch '20131006-dtrace-mdoc' into markj-develop