Firstly, IsFormat is unused so there's no "escape" of
bFmt back into the outside world.

Then bFmt has two purposes.

Purpose 1 is 'not be a format dialog, be a format dialog, be a format dialog but hide standard button'

so, lets just add an explicit "Hide standard button" method and call
it in the (apparently) one place where it's necessary.

Purpose 2 is to flag that "BaseFmtHdl" was called from clicking
the "Standard" button at which point its set to 2.

SfxTabDialog::Init_Impl had...

"
  // bFmt = temporary Flag passed on in the Constructor(),
  // if bFmt == 2, then also sal_True,
  // additional suppression of the standard button,
  // after the Initializing set to sal_True again
  if ( bFmtFlag != 2 )
      m_pBaseFmtBtn->Show();
  else
      bFmtFlag = sal_True;
"

but the variable acted on is bFmtFlag a copy of bFmt, and is never read again
after that line, so setting it to sal_True is meaningless. The comment suggests
that the intent is to reset bFmt to true if it was 2 during initialization,
which fits with the later use of bFmt == 2 to indicate that the standard button was
clicked, i.e. reset bFmt back to its standard value.

So make bFmt a simple toggle of dialog as a format dialog or not, add a way
to remove the standard button and add a second variable to indicate the standard
button got pressed.

Change-Id: I98a441f5f314845abe243e05b6d92fd71d7b0b04