Release notes for 2020-08-22   (SVN r2141)
Updates since 2020-07-12.  See ReleaseNotes_20200712.txt for earlier updates.

This is mostly a minor bugfix/cleanup release.

---------------
 New features:
---------------

*   jzIntv
    *   Debugger improvements:  (Readline-enabled builds only)
        *   Execute keyboard map changes immediately when in the debugger.
        *   When switching keymaps, refresh the command prompt cleanly.


----------
 Changes:
----------

*   Upgrades to Cheat facility:
    *   Cheat facility now supports up to 32 cheats.
    *   Cheats can be assigned numbers explicitly on the command line with
        --cheat<#>="details".  e.g. --cheat17="p 123 45"
    *   Cheat startup messages go to stdout now, instead of stderr.
    *   Termux Makefiles now forward to main Linux Makefiles, after loading
        Termux-specific configuration details.

-------------------------
 Cleanups and bug fixes:
-------------------------

*   Improvements:
    *   Add new PLAT_xxx macros that are zero/non-zero valued, rather than
        defined/not-defined.
    *   Use _WIN32, not WIN32 to identify Windows.  Migrate jzIntv code to
        use PLAT_WIN32 for jzIntv's code.
    *   Start migrating away from #ifdef and toward "constant if" statements.
    *   Replace USE_SDL2 macro with USE_SDL={0,1,2} definition.  
        *   Numerous minor cleanups throughout source, esp. event_tbl.inc.
        *   This is part of migrating away from separate Makefiles for SDL1
            and SDL2.  Eventually, this should help catch places we include
            sdl_jzintv.h when we shouldn't.
    *   Clean up event_sdl.c to better isolate system differences and
        SDL1/SDL2 differences.
    *   Add "include guards" on some buildcfg/ files to make it easier to
        write top-level Makefiles that explicitly include specific
        configuration files for some aspects, but rely on buildcfg/* for the
        rest.

*   Fixed bugs:
    *   Fix "stuck in Map 3" issues.  Keyboard stack was not initialized
        correctly, and could get jzIntv stuck in Map 3.
    *   Return 0 on clean exit, rather than 1.

*   Misc:
    *   On Linux w/X11, attempt to delete the WM_TRANSIENT_HINT property
        from our window if SDL set it when we didn't want it.  This code is
        currently very "chatty."  I expect to make it less so in the future.
    *   Remove some more unused Makefiles.
    *   Disable -Wunreachable-code for Clang builds, as there's no way to teach
        it to ignore intentional "if (0)" constructs.