Revert "syscall: Moved syscall_table into arch/"

This reverts commit 19cf3a75be31b70225741e1ce0f1d87dcb69cc37.
proc: change thread struct registers to be pointer instead of static struct
x86: move {PUSH,POP}_REGISTERS into macros.S
syscall: store user regs on all system calls
make: parallelize kernel build with 8 jobs