Add discover.cc to libmysqld Makefile

libmysqld/Makefile.am:
  Add the new file discover.cc to Makefile.am in libmysqld/ dir to make it be symlinked and built for embebedded server.

libmysqld/Makefile.am

@@ -48,7 +48,7 @@ sqlsources = derror.cc field.cc field_conv.cc strfunc.cc filesort.cc \
 	key.cc lock.cc log.cc log_event.cc sql_state.c \
 	protocol.cc net_serv.cc opt_range.cc \
 	opt_sum.cc procedure.cc records.cc sql_acl.cc \
-	sql_load.cc sql_olap.cc \
+	sql_load.cc sql_olap.cc discover.cc \
 	sql_analyse.cc sql_base.cc sql_cache.cc sql_class.cc \
 	sql_crypt.cc sql_db.cc sql_delete.cc sql_error.cc sql_insert.cc \
 	sql_lex.cc sql_list.cc sql_manager.cc sql_map.cc sql_parse.cc \