When the DCD is disabled the modem does not hangup anymore after the
data connection. This allows for simpler connection handling and it
allows to remove all TTY hangup work-arounds.
This patch was generated by the following semantic patch
(http://coccinelle.lip6.fr/)
// <smpl>
@fix disable is_null,isnt_null1@
expression *E;
@@
- !E
+ E == NULL
// </smpl>