Removed IRQ support from TGI drivers.

All but one TGI drivers didn't use IRQs. Especially when the TGI driver kernel was the only .interruptor this meant quite some unnecessary overhead because it pulled in the whole IRQ infrastructure.

The one driver using IRQs (the graphics driver for the 160x102x16 mode on the Lynx) now uses a library reference to set up a JMP to its IRQ handler.

libsrc/lynx/tgi_irq.s

@@ -0,0 +1,11 @@
+;
+; Oliver Schmidt, 2018-02-02
+;
+
+        .export         tgi_libref
+        .interruptor    tgi_irq         ; Export as IRQ handler
+
+        .data
+
+tgi_libref:
+tgi_irq:        .byte   $60, $00, $00   ; RTS plus two dummy bytes