common: Use new function to print status strings.

* common/asshelp2.c (vprint_assuan_status_strings): New.
(print_assuan_status_strings): New.
* agent/command.c (agent_write_status): Replace by call to new
function.
* dirmngr/server.c (dirmngr_status): Ditto.
* g13/server.c (g13_status): Ditto.
* g13/sh-cmd.c (g13_status): Ditto.
* sm/server.c (gpgsm_status2): Ditto.
* scd/command.c (send_status_info): Bump up N.

This fixes a potential overflow if LFs are passed to the status
string functions. This is actually not the case and would be wrong
because neither the truncating in libassuan or our escaping is not the
Right Thing. In any case the functions need to be more robust and
comply to the promised interface. Thus the code has been factored out
to a helper function and N has been bumped up correctly and checked in
all cases.

For some uses this changes the behaviour in the error case (i.e. CR or
LF passed): It will now always be C-escaped and not passed to
libassuan which would truncate the line at the first LF.

• Reported-by: private_pers