[9front] [PATCH] manual: preprocess usb(3) with eqn for print output

[Anthony Martin <ality@pbrane.org>]

igor@9lab.org reported that the eqn directive
"delim $$" was appearing at the top of the
printed manual page for usb(3). This was due
to a lack of preprocessing for this specific
file.

All other files are accounted for:

	% cd /sys/man
	% for(i in TS EQ PS G1) echo $i `{grep -l '^\.'$i ?/[0-9a-z]*}
	TS 1/tbl
	EQ 1/eqn 3/usb
	PS 1/pic
	G1 1/grap
	%

Note that 1/pic does not currently need to
be preprocessed because the examples were
inadvertently elided when removing the tpic
command. That should be corrected in a later
patch.

---
diff 065cf0b708be75e84e568261a044d66286ef6e3d fc0732aa11564503810cd76e84f267d18ee97220
--- a/sys/man/mkfile	Sun Jun 20 20:56:14 2021
+++ b/sys/man/mkfile	Mon Jun 21 01:23:43 2021
@@ -24,7 +24,7 @@
 				switch($i/$j){
 				case 1/tbl
 					tbl $j
-				case 1/eqn 3/realtime 6/auth
+				case 1/eqn 3/usb
 					eqn $j
 				case 1/pic
 					pic $j