Add JEMALLOC_FORMAT_PRINTF().

Replace JEMALLOC_ATTR(format(printf, ...). with
JEMALLOC_FORMAT_PRINTF(), so that configuration feature tests can
omit the attribute if it would cause extraneous compilation warnings.

include/jemalloc/jemalloc_defs.h.in

@@ -4,6 +4,12 @@
 /* Defined if alloc_size attribute is supported. */
 #undef JEMALLOC_HAVE_ATTR_ALLOC_SIZE
 
+/* Defined if format(gnu_printf, ...) attribute is supported. */
+#undef JEMALLOC_HAVE_ATTR_FORMAT_GNU_PRINTF
+
+/* Defined if format(printf, ...) attribute is supported. */
+#undef JEMALLOC_HAVE_ATTR_FORMAT_PRINTF
+
 /*
  * Define overrides for non-standard allocator-related functions if they are
  * present on the system.