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`.

2005/jetro/Makefile

@@ -86,7 +86,7 @@ ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 CSILENCE+= -Wno-cast-align -Wno-comma -Wno-double-promotion -Wno-missing-prototypes \
 	-Wno-missing-variable-declarations -Wno-padded \
 	-Wno-poison-system-directories -Wno-shadow -Wno-shorten-64-to-32 \
-	-Wno-unused-macros
+	-Wno-unused-macros -Wno-documentation-unknown-command
 #
 CWARN+= -Weverything
 #