silence most warnings under macOS

For macOS Apple clang version 15.0.0 (clang-1500.3.9.4)
compiler, we have silenced the warnings that can be silenced.

We also updated `.gitignore` for `2014/maffiodo2` and `1995/vanschnitz`.

2004/jdalbec/Makefile

@@ -39,7 +39,7 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-int-to-pointer-cast -Wno-int-to-void-pointer-cast -Wno-trigraphs \
-	-Wno-unused-value
+	-Wno-unused-value -Wno-gnu-line-marker
 
 # Common C compiler warning flags
 #