Add -console option on Windows

This adds the `-console` command-line option (for Win32 only) so the
game can spawn an attached console window which will contain all console
output.

This is to make it easier for people to debug on Windows systems.
Otherwise, the only way to get console output would be to either compile
the application as a console app (i.e. switch the subsystem to console)
- which is undesirable for regular users as this makes it so a console
is always spawned even when unwanted - or launch the game with shell
arguments that make it so output is redirected to a file.

As a result, color checking support is factored out of vlog_init() into
its own function, even though we don't support colors on Windows.

desktop_version/src/Vlogging.h

@@ -10,6 +10,10 @@ extern "C"
 
 void vlog_init(void);
 
+#ifdef _WIN32
+void vlog_open_console(void);
+#endif
+
 void vlog_toggle_output(int enable_output);
 
 void vlog_toggle_color(int enable_color);