Bug fixes; get mouse working.

Fix bug in post causing PIC2 to not be initialized properly.
Only run ata_detect if CONFIG_ATA enabled.
Improve debugging aids - introduce debug_isr(); move DEBUGF to each file.
Enable mouse by default.
Fix bug in floppy causing extra test of PORT_FD_STATUS on recalibrate.
Always disable/enable kbd in handle_09 event.
diff --git a/src/boot.c b/src/boot.c
index 19a4929..1ab9423 100644
--- a/src/boot.c
+++ b/src/boot.c
@@ -183,7 +183,8 @@
 void VISIBLE
 begin_boot()
 {
-    ata_detect();
+    if (CONFIG_ATA)
+        ata_detect();
     irq_enable();
     struct bregs br;
     memset(&br, 0, sizeof(br));