FMSLogo Code

Fix some minor issues with the "restart with good aspect ratio" logic.
1) An IF that was used as an IFELSE is now an IFELSE.
2) The -H parameter was given with a decimal point (which was then
ignored due to compatibility with historically sloppy command line
parsing. The -H command-line parameter is now given as an INT.
3) The command line to run manually (when automatic restart fails) is now
given on a separate line for readability.

None of these issues prevented the code from doing what it was supposed to do.

Fix some problems with the implementation of SHELL on non-Microsoft platforms
1) When executed synchronously, it will does not freeze the UI (although it still can't be halted)
2) When executed asynchronously, the return code is calculated correctly (although it always seems to be true)

Fix the name of the bitmap file so that the case exactly matches the file.
This fixes a problem where it couldn't load the bitmap on GNU/Linux, where the file system is case-sensitive.

Revert the changes that implemented LABEL in pure wxWidgets API on MSW.
This was done to avoid a breaking change in the way line breaks are handled.
wxWidgets doesn't handle line break uniformly (LABELSIZE still ignores them and some fonts treat it as a carriage return, not a newline). Rather than have better but inconsistent behavior, I opted for the status quo.

Cleanup: remove some unnecessary casting to native handles
The wxWidgets API was designed to avoid the need for the client to explicitly cast.

Fix a build break introduced in the previous revision

Replace a call to the win32 MessageBox API with wxMessageBox.
This enables the message box to appear on GNU/Linux.

Get enough of SETFOCUS and WINDOWSET working on GNU/Linux to play snake.lgo.
This amounts to being able to MINIMIZE the commander and SETFOCUS on the screen window.

Implement MyMessageScan on non-MSW platforms using wxWidgets API.
Among other things, this enables the drawing to be seen as drawing instructions are run, instead of only appearing the next time control flow reaches the top level. For example, this enables the game play of the snake.lgo program in the "extras" project.

Fix a build break on GNU/Linux when precompiled headers aren't used.