silence warnings under macOS for cc, clang and gcc

Used the following script to check for warnings
not silenced via ${CSILENCE}:

```sh
find ???? -mindepth 1 -maxdepth 1 -type d | while read dir; do
(cd "$dir"; echo =-=-= "$dir" =-=-= ; csilence -v 1 clobber all ; echo ; csilence -v 1 clobber alt)
done 2>&1 | less
```

1995/garry/Makefile

@@ -38,7 +38,8 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-extra-semi -Wno-fortify-source -Wno-return-type
+CSILENCE= -Wno-extra-semi -Wno-fortify-source -Wno-return-type -Wno-strict-prototypes \
+	-Wno-unused-variable
 
 # Common C compiler warning flags
 #