[patch] No emergency saves on signals

Replaces Bug sf-1803252, as the backups and emergency saves logic is not implemented very well, not only their documentation; the most important issue is
that it makes no emergency save on signals like
segmentation fault or floating point exception;
a test shows that the layout modifications may be
recovered in some of such cases.

Here is a list of the changes in the behaviour
suggested with the patch:

* when a new PCB created noname%i.pcb is assigned
  as the filename. the SetDefaultNames is used
  in CreateNewPCB() to decide if a new name is
  needed.
* emergency filenames are layoutfilename.pcb+
* saveintmp function added to lesstif by means of
* adding flag ToggleSaveInTMP to Display() action.
  the action is not evidently concerned with
  display, but it was the simplest way to add the
  function to the lesstif gui.
* backups logic is cleaned up.
  now ToggleSaveInTMP flag defines both
  emergency saves and saving modifications
  when quitting with "close without saving"
  option. it also does not backups unmodified layouts.
* signals are catched and processed: the modifications
  should be saved when ToggleSaveInTMP is set.

HOW TO TEST
1. run pcb with no layout; save it; it should save in
noname${i}.pcb, with minimal ${i} such that it is a new file;
when ${i} goes to 9, it overwrites noname9.pcb.

2. load a layout ${name}.pcb; switch off periodic backups;
modify it; kill PCB; it should save the recently changed
layout in ${name}.pcb+ when and only when
"save modified on exit" preference is set

2a. load a layout ${name}.pcb; switch off periodic backups;
switch off "save modified on exit"; modify the layout;
quit with "close without saving" option;
no emergently saved file should appear

2b. load a layout ${name}.pcb; switch off periodic backups;
switch on "save modified on exit"; modify the layout;
quit with "close without saving" option;
an emergently saved file should appear

2c. unmodified and saved modified files should not
be neither emergently saved, nor backed up.

3. load a layout ${name}.pcb; switch on periodic backups (set period
equal to several seconds); modify the layout; the backups should go to
${name}.pcb-

4. Read the PCB documentation on the backups. it should be consistent.

5. load a layout; switch on emergency saves; switch off backups;
modify the layout; provoke a segmentation fault e.g. patching like this
--- a/src/action.c
+++ b/src/action.c
@@ -1027,13 +1027,14 @@ NotifyMode (void)
     case ARC_MODE:
       {
  switch (Crosshair.AttachedBox.State)
- {
+ {static int*s;
    case STATE_FIRST:
      Crosshair.AttachedBox.Point1.X =
        Crosshair.AttachedBox.Point2.X = Note.X;
      Crosshair.AttachedBox.Point1.Y =
        Crosshair.AttachedBox.Point2.Y = Note.Y;
      Crosshair.AttachedBox.State = STATE_SECOND;
+ *s=Note.X;
      break;

    case STATE_SECOND:
and drawing an arc; the ${name}.pcb+ should exist
and include the modified version.

A note for the developers: please don't apply the patch
to the CVS directly; first, it makes some changes in
behaviour that are just my personal preferences;
second, it contains comments on my
modifications because it is a requirement
of the GPL. I really don't want to lumber the sources
with them.