Note limitation of parse_rfc_1123_time

RFC1123 suggests that we should handle two-year times, and a full
range of time zones, and other stuff too.  We don't.

src/common/util.c

@@ -1408,6 +1408,9 @@ format_rfc1123_time(char *buf, time_t t)
 /** Parse the (a subset of) the RFC1123 encoding of some time (in UTC) from
  * <b>buf</b>, and store the result in *<b>t</b>.
  *
+ * Note that we only accept the subset generated by format_rfc1123_time above,
+ * not the full range of formats suggested by RFC 1123.
+ *
  * Return 0 on success, -1 on failure.
 */
 int