Update .gitignore

.gitignore

@@ -9,6 +9,7 @@
 Makefile
 /BUILD/
 /UNUSED/
+/DISK/
 
 # Prerequisites
 *.d
@@ -43,3 +44,7 @@ Makefile
 *.out
 *.app
 
+# Disk image files
+*.img
+*.iso
+*.fd