Kernel/LibC: Add bareboness signals

You can now call raise() to raise a signal. Signal handlers are
not yet supported, but the handling works :)

kernel/include/kernel/Process.h

@@ -100,6 +100,10 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_alloc(size_t);
 		BAN::ErrorOr<long> sys_free(void*);
 
+		BAN::ErrorOr<long> sys_signal(int, void (*)(int));
+		BAN::ErrorOr<long> sys_kill(pid_t pid, int signal);
+		BAN::ErrorOr<long> sys_raise(int signal, uintptr_t& return_rsp, uintptr_t& return_rip);
+
 		BAN::ErrorOr<long> sys_termid(char*) const;
 
 		BAN::ErrorOr<long> sys_clock_gettime(clockid_t, timespec*) const;