added installer.nsi

git-svn-id: http://haxe.googlecode.com/svn/trunk@6595 f16182fa-f095-11de-8f43-4547254af6c6
use native sys_getch

git-svn-id: http://haxe.googlecode.com/svn/trunk@6596 f16182fa-f095-11de-8f43-4547254af6c6