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
```

2000/briddlebane/Makefile

@@ -38,8 +38,9 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-absolute-value -Wno-implicit-int \
-	-Wno-incompatible-function-pointer-types -Wno-unsequenced
+CSILENCE= -Wno-absolute-value -Wno-implicit-int -Wno-deprecated-non-prototype \
+	-Wno-incompatible-function-pointer-types -Wno-unsequenced \
+	-Wno-strict-prototypes
 
 # Common C compiler warning flags
 #