GitLab

Detail:
  I keep finding declarations of the Toolbox SWI symbols all over the
    place.  These header files provide a single definition for the SWIs
    for the Toolbox and Window modules.
Admin:
  Exported from Common because Libs is too awkward to modify just for
    this change (it uses Makatic).

Tided up the make process for the libraries tboxlib and debuglib (debuglib was in with the same set of sources as tboxlib to I build it anyway).

All header files in the objects directory now get exported to
<Lib$Dir>.tboxlibs.h during export_hdrs phase. tboxlib and debuglib get build
with both zM and none zM flags and exported to <Lib$Dir>.tboxlibs.o.

Changed the sources slightly so they don't refer to the internal copy of the
header files found in objects but the copy previously exported to the right
place.