muscle: Also add headers to the _devel package

I'm not sure which ones we need, so I'll put them all for now.

net-misc/muscle/muscle-6.00.recipe

@@ -63,7 +63,17 @@ INSTALL()
 	cp muscled $binDir
 	cp admin $binDir/muscled-admin
 
+	mkdir -p $developLibDir
+	mkdir -p $includeDir/muscle
+
 	cp libmuscle.a $developLibDir
+	cd ..
+	#XXX: do we really need all of those?
+	for d in message besupport dataio iogateway reflector regex \
+		util syslog system zlib zlib/zlib; do
+		mkdir -p $includeDir/muscle/$d
+		cp $d/*.h $includeDir/muscle/$d
+	done
 	packageEntries devel \
 			$developDir
 }