FMSLogo Code

Finish fixing bug #373 (give screensaver command parity with main environment). This revision enables WINDOWCREATE and DIALOGCREATE by providing a way for them to set the "always on top" flag, which is needed so that the dialog boxes and windows stay on top of the screensaver.

Change the type of a scroll position from UNIT to int. UNIT is a Windows-specific type and was used because the OWL version of FMSLogo used it. Now that the OWL version has been deleted, it's more natural (and platform-independent) to use what wxWidgets uses, which is int.

For consistency, change the text of "espacio de trabajo" to "area de trabajo",
change some imperitivates to the intimate "tu" form, and change "por lo que"
to "por lo tanto". These were originally translated by me (a non-native speaker)
and I probably relied too much on machine translation.

Fix a build break on GNU/Linux that resulted from unifying the logic in
CScreen:::OnPaint with the logic in PaintToScreenWindow() that was used
exclusively by the Windows screensaver. I had put the new function in
a file that was not compiled into the GTK version. This revision adds
that file (mainwind.cpp) into the GTK build.

Fix build breaks on GNU/Linux that resulted from changing the type of
the scrollbar positions from "UINT" to "int". The change was incomplete
and this revision completes the change.

Add some missing "const" qualifiers to fix compiler warnings with gcc (same as with the other .xpm files)

Change the type of a scroll position from UNIT to int. UNIT is a Windows-specific type and was used because the OWL version of FMSLogo used it. Now that the OWL version has been deleted, it's more natural (and platform-independent) to use what wxWidgets uses, which is int.

Combine the logic within CScreen::OnPaint() and PaintToScreenWindow() so that there's a single function which works for both the full FMSLogo environment and the screen saver. This became possible once both environments stated to use wxWidgets.

Remove the platform-dependent code from ShowMessage() so that it can be called correctly on non-Windows platforms.

Fix bug #437; FMSLogo no longer crashes if BITMAPTURTLE has no bitmap (it now behaves as if it had a zero-sized bitmap)