Allow for warning-free build of libraries.

libsrc/dbg/dbg.c

@@ -518,6 +518,10 @@ static char IsAbortKey (char C)
     if (C == CH_STOP) {
         return 1;
     }
+#endif
+#if !defined(CH_ESC) && !defined(CH_STOP)
+    /* Avoid compiler warning about unused parameter */
+    (void) C;
 #endif
     return 0;
 }