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`.

1989/westley/Makefile

@@ -42,7 +42,9 @@ CSILENCE= -Wno-comment -Wno-error -Wno-implicit-function-declaration \
 	-Wno-logical-op-parentheses -Wno-deprecated-non-prototype \
 	-Wno-int-conversion -Wno-return-type -Wno-parentheses \
 	-Wno-comma -Wno-missing-variable-declarations -Wno-unused-value \
-	-Wno-implicit-int -Wno-missing-parameter-type -Wno-pointer-to-int-cast
+	-Wno-implicit-int -Wno-missing-parameter-type -Wno-pointer-to-int-cast \
+	-Wno-conditional-type-mismatch -Wno-non-literal-null-conversion \
+        -Wno-unknown-warning-option
 
 # Common C compiler warning flags
 #