Add --log-debug to man page.

man/dnsmasq.8

@@ -154,6 +154,9 @@ allows the log file to be rotated without stopping dnsmasq.
 .B --log-debug
 Enable extra logging intended for debugging rather than information.
 .TP
+.B --log-malloc
+Enable logging of memory allocation and release, for debugging.
+.TP
 .B --log-async[=<lines>]
 Enable asynchronous logging and optionally set the limit on the
 number of lines