sched: add POSIX signal support

We have added POSIX signals to KirkOS

It is very much experimental

Alongside, we have PCI support fully, and we have imported sbase coreutils, I'm not too sure if all of them work, likely not, but a good few should be okay.

Signed-off-by: kaguya <kaguya3311@national.shitposting.agency>

src/arch/x86_64/serial/serial.h

@@ -7,4 +7,16 @@ void serial_putchar(char ch);
 void serial_puts(char *str);
 char serial_get_byte(void);
 char serial_getchar(void);
-int serial_received(void);
+int serial_received(void);
+
+
+/* Mask the UART receive-data-available IRQ (IER bit 0). Used by the
+ * breakpoint debugger so bytes typed while it polls serial_getchar() are
+ * not silently consumed by serial_irq_handler() and pushed into the input
+ * ring instead of being delivered to the debugger. */
+void serial_disable_rx_irq(void);
+
+/* Re-arm the UART receive-data-available IRQ and drain anything that
+ * accumulated in the RBR while the IRQ was masked. Mirror of
+ * serial_disable_rx_irq(). */
+void serial_enable_rx_irq(void);