Merge branch 'refactor-syntax_unicode' into refactor-syntax_unicode_mac

Conflicts:
	engine/src/dskmain.cpp
Make sure we clear globals on desktop.
IO_header suppressed, MCSystemFileHandle now directly used.
Note: legacy code using IO_WRITTEN/IO_SEEKED flags has been commented out using #ifdef OLD_IO_HANDLE macro
Merge remote-tracking branch 'origin/refactor-syntax_unicode_mac' into refactor-syntax_unicode_mac

Conflicts:
	engine/src/dskmain.cpp