init: add 'enable <service>' to negate "service <service>... disabled"

enable <servicename>
   Turns a disabled service into an enabled one as if the service did not
   specify disabled in the rc file.
   It will also start the service if needed.

Bug: 14472973
Change-Id: Id0b49cc687a2bc74f6f92e066c617724cc94908d
Signed-off-by: JP Abgrall <jpa@google.com>
diff --git a/init/keywords.h b/init/keywords.h
index 97fe50c..6625330 100644
--- a/init/keywords.h
+++ b/init/keywords.h
@@ -6,6 +6,7 @@
 int do_class_stop(int nargs, char **args);
 int do_class_reset(int nargs, char **args);
 int do_domainname(int nargs, char **args);
+int do_enable(int nargs, char **args);
 int do_exec(int nargs, char **args);
 int do_export(int nargs, char **args);
 int do_hostname(int nargs, char **args);
@@ -55,6 +56,7 @@
     KEYWORD(critical,    OPTION,  0, 0)
     KEYWORD(disabled,    OPTION,  0, 0)
     KEYWORD(domainname,  COMMAND, 1, do_domainname)
+    KEYWORD(enable,      COMMAND, 1, do_enable)
     KEYWORD(exec,        COMMAND, 1, do_exec)
     KEYWORD(export,      COMMAND, 2, do_export)
     KEYWORD(group,       OPTION,  0, 0)