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`.

1993/jonth/Makefile

@@ -42,7 +42,7 @@ CSILENCE= -Wno-error -Wno-implicit-function-declaration \
 	-Wno-incompatible-pointer-types -Wno-int-conversion \
 	-Wno-c99-extensions -Wno-deprecated-declarations \
         -Wno-deprecated-non-prototype -Wno-format -Wno-pedantic -Wno-return-type \
-        -Wno-strict-prototypes -Wno-unused-variable
+        -Wno-strict-prototypes -Wno-unused-variable -Wno-implicit-int
 
 # Common C compiler warning flags
 #