sys/linux: Add binding to ioctl syscall + fd consts

Add binding to ioctl syscall, due to the vast nature of this syscall
adding more device specific request values is possible. Also added the
stdin, stdout and stderr, to constants.odin

core/sys/linux/constants.odin

@@ -1,6 +1,21 @@
 
 package linux
 
+/*
+	Standard input file descriptor
+*/
+STDIN_FILENO :: Fd(0)
+
+/*
+	Standard output file descriptor
+*/
+STDOUT_FILENO :: Fd(1)
+
+/*
+	Standard output file descriptor
+*/
+STDERR_FILENO :: Fd(2)
+
 /*
 	Special file descriptor to pass to `*at` functions to specify
 	that relative paths are relative to current directory.

core/sys/linux/sys.odin

@@ -216,7 +216,17 @@ rt_sigprocmask :: proc "contextless" (mask_kind: Sig_Mask_Kind, new_set: ^Sig_Se
 	return Errno(-ret)
 }
 
-// TODO(flysand): ioctl
+/*
+	Control devices. The ioctl syscall is a bit special because
+	its argument is usually a pointer to some driver-specific structure.
+	The request value is device-specific. Consult your LibC implementation's
+	ioctls.h file to learn more.
+	Available since Linux 1.0.
+*/
+ioctl :: proc "contextless" (fd: Fd, request: u64, arg: u64) -> (Errno) {
+	ret := syscall(SYS_ioctl, fd, request, arg)
+	return Errno(-ret)
+}
 
 /*
 	Read the file at a specified offset.