FMSLogo Code

Change the way the turtle's lines are drawn in the common case.
This changes them from a series of line segments to a path (continuous segments).

The primary motivation for this change was to fix a regression introduced by upgrading to wxWidgets 3.1.3 where the bottom line of the turtle was white on startup and in a few other places. I didn't track down what caused this, but instead noticed that using wxDC::DrawLines() didn't have this problem.

I was hoping this would also improve drawing time when the turtle is shown, as there are fewer points to calculate and draw, but BENCHMARK showed no improvement.

Note that, in PERSPECTIVE mode, the turtle can be partially on-screen, which means that the turtle's shape is not continuous, but may be broken line segments. Because of this, the turtle retains the old segment-based drawing behavior as a fall-back.

Undo side-effects in SPRITEPERFTEST of hiding turtle and zooming.
This was done so that running BENCHMARK twice in a row gives similar results.

Fix a leak in BENCHMARK.PLIST.
Instead of erasing the property list, it erased a variable with the name of the property list(which didn't exist).

Fix a build break when using wxWidgets 3.0.4.
Apparently wxSTC_KEYMOD_CTRL hasn't been back-ported to the 3.0.X branch.

Update FMSLogo to from wxWidgets 3.1.0 to wxWidgets 3.1.3.

The main reason for this is to get a bug fix for Unicode command line processing that will enable me to remove a hack in fmslogo.cpp. However, it's also good to stay up-to-date on libraries to minimize the number of problems caused by each upgrade.

This library update cooresponds with a major version number increase in FMSLogo from 7.7.0 to 8.0.0. It's good to include a potentially disruptive change to a library in major version increase, since it's somewhat expected that things will be incompatible and possibly be broken.

Remove gbm_guess_filetype() and extension().
These used deprecated forms of wcstok() which are not available in modern C++. More importantly, they caused build errors when compiling on GNU/Linux.
Fortunately, neither of these functions were used by FMSLogo, so it was easier to remove them than to fix them.

Change wxSTC_SCMOD_CTRL to wxSTC_KEYMOD_CTRL.
wxSTC_SCMOD_CTRL is deprecated in wxWidgets 3.1.3.

Call SetCursor directly form OnSetCursor() instead of calling into lsetcursorarrow()
Calling into the Logo engine, which then called back into CMainFrame was not only convoluted, but also causes a shutdown crash on wxWidgets 3.1.3.

Fix minor typos (missing period, wrong tense)

Remove the "unicode" branch, now that it's be integrated into trunk.