Add remaining missing syscalls back and fix some warnings
Fix ndless_installer and add some more Zehn features

-utils.c now symlinked and compiled seperately for installer and resources
-Make ndless_installer smaller by leaving out syscall-addrs.h in utils.c
-Treat backwards-compatible Zehn files (make-prg) as normal Zehn applications
-Show Zehn information by pressing KEY_NSPIRE_CAT at executable start