FMSLogo Code

Add TIMERTEST.OVERWRITE to test that calling SETTIMER twice in a row implicitly calls CLEARTIMER on the first timer.
I don't know if this is intentional behavior, but it's how MSWLogo behaved so it should be preserved for compatibility.

Remove some explicit uses of static_cast<>() to cast to native handles.
The wxWidgets API is set up to do this cast implicitly.

Fix build breaks when compiling the screen saver that were introduced by recent changes to LABEL and LABELSIZE.

#include fontutils.h from fontutils.cpp.
It's a good practice to include the interface that you're implementing.

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