Kernel/LibC: Rework userspace syscall interface

Kernel syscall API no longer zeros all unused argument registers and
libc now uses inlined syscall macro internally. This significantly
cleans up generated code for basic syscall wrapper functions.

kernel/kernel/Syscall.cpp

@@ -7,6 +7,7 @@
 #include <kernel/Timer/Timer.h>
 
 #include <termios.h>
+#include <sys/syscall.h>
 
 #define DUMP_ALL_SYSCALLS 0
 #define DUMP_LONG_SYSCALLS 0