devdraw: plumb drag-n-dropped files

Change-Id: I7585870aee57c7482ebdd19c117be7982123ce79
Reviewed-on: https://plan9port-review.googlesource.com/1130
Reviewed-by: Russ Cox <rsc@google.com>

bin/macedit

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+PLAN9=${PLAN9:-/usr/local/plan9}
+bin=$PLAN9/bin
+
+file=$1
+
+# Blanks are problematic in filenames: just plumb
+# the file's content.
+if echo "$file" | grep -q " "
+then
+	base=$(basename "$file" | sed 's/ /_/g')
+	attr="action=showdata filename=/BadName/$base"
+	cat $file | "$bin/plumb" -i -d edit -a "$attr"
+else
+	"$bin/plumb" -d edit "$file"
+fi