Re: bsd.port.mk.5: Improve checkpatch description

PATCH_DEBUG is already the default as mentioned in the beginning
bsd.port.mk(5), the `patch' target description does not speak of
debugging information itself so I find it a bit irretating that
`checkpatch' is described as "Debugging version".

New wording is snatched from patch(1)'s `-C', which is all that
`checkpatch' really does. This also makes it a tad clearer/more explicit
that WRKSRC will not be modified.

Feedback?

PS: This only makes sense once the target itself is fixed, of course.

Index: bsd.port.mk.5
===================================================================
RCS file: /cvs/src/share/man/man5/bsd.port.mk.5,v
retrieving revision 1.479
diff -u -p -r1.479 bsd.port.mk.5
--- bsd.port.mk.5 8 May 2018 08:03:59 -0000 1.479
+++ bsd.port.mk.5 25 May 2018 07:31:36 -0000
@@ -150,10 +150,7 @@ Apply
.Cm check-register
to all subpackages of the current port.
.It Cm checkpatch
-Debugging version of the
-.Cm patch
-target that simulates invoking
-.Xr patch 1 .
+Check that patches would apply cleanly, but do not modify anything.
.It Cm checksum
Compute a
.Xr sha256 1