Syscalls

[ebsksjk]

As it is now possible to call arbitrary executables, we now need syscalls to build a small stdlib to write more usable programs

Outline:

• implement Interrupts
• implement Traps to execute kernel code when an interrupt is used
• implement argument passing (stack ig)
• implement syscall for print()
• implement syscall for read()
• implement syscall for open()
• bundle all in venera_std.h