Fix missing UNIV_INTERN on dict_table_check_foreign_keys().

When UNIV_INTERN is missing in built-in XtraDB, this causes the
innodb_plugin to call the XtraDB version of the function instead
of its own (seen in --embedded-server test failure in Buildbot).
This in turn causes bad things to happen in case of difference
between XtranDB and innodb_plugin.

storage/innobase/dict/dict0load.c

@@ -2512,6 +2512,7 @@ contain the same set of foreign key objects; and check if
 dict_table_t::referenced_rbt and dict_table::referenced_list contain
 the same set of foreign key objects.
 @return	TRUE if correct, FALSE otherwise. */
+UNIV_INTERN
 ibool
 dict_table_check_foreign_keys(
 /*==========================*/

storage/xtradb/dict/dict0load.c

@@ -2586,6 +2586,7 @@ contain the same set of foreign key objects; and check if
 dict_table_t::referenced_rbt and dict_table::referenced_list contain
 the same set of foreign key objects.
 @return	TRUE if correct, FALSE otherwise. */
+UNIV_INTERN
 ibool
 dict_table_check_foreign_keys(
 /*==========================*/