switch editors/* to embedded-in-source kbuild system

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

editors/ed.c

@@ -7,6 +7,18 @@
  * The "ed" built-in command (much simplified)
  */
 
+//config:config ED
+//config:	bool "ed"
+//config:	default y
+//config:	help
+//config:	  The original 1970's Unix text editor, from the days of teletypes.
+//config:	  Small, simple, evil. Part of SUSv3. If you're not already using
+//config:	  this, you don't need it.
+
+//kbuild:lib-$(CONFIG_ED) += ed.o
+
+//applet:IF_ED(APPLET(ed, BB_DIR_BIN, BB_SUID_DROP))
+
 //usage:#define ed_trivial_usage ""
 //usage:#define ed_full_usage ""