Redirect gs stdout to stderr. This will prevent warnings to be part of

the generated file causing broken files.  This does not redirect drivers
output which still write to stdout.

I'm currently seeing "**** Warning: glyf overlaps cmap, truncating."
during esptopng conversion leading to broken .pnm.
This change prevents the broken .pnm file.

share/mk/doc.commands.mk

@@ -117,7 +117,7 @@ SCR2PNGOPTS?=	${SCR2PNGFLAGS}
 SCR2TXT?=	${PREFIX}/bin/scr2txt
 SCR2TXTOPTS?=	-l ${SCR2TXTFLAGS}
 EPS2PNM?=	${PREFIX}/bin/gs
-EPS2PNMOPTS?=	-q -dBATCH -dGraphicsAlphaBits=4 -dTextAlphaBits=4 \
+EPS2PNMOPTS?=	-sstdout=%stderr -q -dBATCH -dGraphicsAlphaBits=4 -dTextAlphaBits=4 \
 		-dEPSCrop -r${EPS2PNM_RES}x${EPS2PNM_RES} \
 		-dNOPAUSE -dSAFER -sDEVICE=pnm -sOutputFile=-
 #