Register dep on json in config.m4

Author: nikic

ext/spl/config.m4

@@ -2,3 +2,4 @@ PHP_NEW_EXTENSION(spl, php_spl.c spl_functions.c spl_engine.c spl_iterators.c sp
 PHP_INSTALL_HEADERS([ext/spl], [php_spl.h spl_array.h spl_directory.h spl_engine.h spl_exceptions.h spl_functions.h spl_iterators.h spl_observer.h spl_dllist.h spl_heap.h spl_fixedarray.h])
 PHP_ADD_EXTENSION_DEP(spl, pcre, true)
 PHP_ADD_EXTENSION_DEP(spl, standard, true)
+PHP_ADD_EXTENSION_DEP(spl, json)