*) Rework the set language support, simplify it by using KIWAY. Now any major
frame with a "change language" menu can change the language for all KIWAY_PLAYERs
in the whole KIWAY. Multiple KIWAYs are not supported yet.
*) Simplify "modal wxFrame" support, and add that support exclusively to
KIWAY_PLAYER where it is inherited by all derivatives. The function
KIWAY_PLAYER::ShowModal() is in the vtable and so is cross module capable.
*) Remove the requirements and assumptions that the wxFrame hierarchy always
had PCB_EDIT_FRAME and SCH_EDIT_FRAME as immediate parents of their viewers
and editors. This is no longer the case, nor required.
*) Use KIWAY::Player() everywhere to make KIWAY_PLAYERs, this registers the
KIWAY_PLAYER within the KIWAY and makes it very easy to find an open frame
quickly. It also gives control to the KIWAY as to frame hierarchical
relationships.
*) Change single_top to use the KIWAY for loading a KIFACE and instantiating
the single KIWAY_PLAYER, see bullet immediately above.
*) Add KIWAY::OnKiwayEnd() and call it from PGM_BASE at program termination, this
gives the KIFACEs a chance to save their final configuration dope to disk.
*) Add dedicated FRAME_T's for the modal frames, so m_Ident can be tested and
these modal frames are distinctly different than their non-modal equivalents.
KIWAY_PLAYER::IsModal() is !not! a valid test during the wxFrame's constructor,
so this is another important reason for having a dedicated FRAME_T for each
modal wxFrame.
On balance, more lines were deleted than were added to achieve all this.
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