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/cdua/Makefile

@@ -38,7 +38,8 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-incompatible-library-redeclaration -Wno-main
+CSILENCE= -Wno-incompatible-library-redeclaration -Wno-main \
+	-Wno-deprecated-non-prototype -Wno-format-security -Wno-strict-prototypes
 
 # Common C compiler warning flags
 #
@@ -84,7 +85,8 @@ CC= cc
 ifeq ($(CC),clang)
 #
 CSILENCE+= -Wno-comma -Wno-missing-variable-declarations \
-	-Wno-poison-system-directories -Wno-strict-prototypes
+	-Wno-poison-system-directories -Wno-strict-prototypes \
+	-Wno-format-nonliteral -Wno-sign-conversion
 #
 CWARN+= -Weverything
 #

1995/dodsond1/Makefile

@@ -38,7 +38,8 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-empty-body -Wno-error -Wno-implicit-function-declaration
+CSILENCE= -Wno-empty-body -Wno-error -Wno-implicit-function-declaration \
+	-Wno-strict-prototypes
 
 # Common C compiler warning flags
 #

1995/dodsond2/Makefile

@@ -38,7 +38,8 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-shift-op-parentheses
+CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-shift-op-parentheses \
+	-Wno-strict-prototypes
 
 # Common C compiler warning flags
 #

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
 #

1995/savastio/Makefile

@@ -39,7 +39,7 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-empty-body -Wno-format -Wno-incompatible-library-redeclaration \
-	-Wno-non-literal-null-conversion
+	-Wno-non-literal-null-conversion -Wno-deprecated-non-prototype -Wno-strict-prototypes
 
 # Common C compiler warning flags
 #

1995/schnitzi/Makefile

@@ -39,7 +39,7 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-int-conversion \
-	-Wno-logical-op-parentheses
+	-Wno-logical-op-parentheses -Wno-deprecated-non-prototype
 
 # Common C compiler warning flags
 #

1995/spinellis/Makefile

@@ -38,7 +38,7 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-empty-body
+CSILENCE= -Wno-empty-body -Wno-strict-prototypes
 
 # Common C compiler warning flags
 #

1995/vanschnitz/Makefile

@@ -39,7 +39,7 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-extra-tokens \
-	-Wno-overlength-strings
+	-Wno-overlength-strings -Wno-strict-prototypes
 
 # Common C compiler warning flags
 #