Improve aarch64 support by building everything for both archictectures,

remove incorrect timer frequency set, fix interrupt handler not
restoring stack ptr, handle both user and kernel aborts, remove aarch64
ps2 support, fix ELF code mapped as code making it unwritable, add
assets.rs to handle both arches automatically, make PS2 x86_64
compatible with linux keycodes, always try printing kernel panic to
serial

assets/.gitignore

@@ -1,2 +1,3 @@
 doomgeneric*
 init
+helloworld*