Change CIO_KEY_MOUSE to use an old Amstrad keyboard mouse scancode.

Add an abort "key" which will indicate the user has gone away (ie: closed
the window)

src/conio/keys.h

@@ -44,4 +44,5 @@
 #define CIO_KEY_NPAGE     (0x51 << 8)
 #define CIO_KEY_ALT_F(x)      ((x<11)?((0x67+x) << 8):((0x80+x) << 8))
 
-#define CIO_KEY_MOUSE    0x02ff
+#define CIO_KEY_MOUSE     0x7d00	// This is the right mouse on Schneider/Amstrad PC1512 PC keyboards
+#define CIO_KEY_ABORTED   0x0100	// ESC key by scancode