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
```

1984/decot/Makefile

@@ -40,7 +40,9 @@ include ../../var.mk
 #
 CSILENCE= -Wno-array-bounds -Wno-error -Wno-implicit-function-declaration \
 	-Wno-keyword-macro -Wno-main-return-type -Wno-missing-field-initializers \
-	-Wno-unused-value -Wno-unused-variable
+	-Wno-unused-value -Wno-unused-variable -Wno-deprecated-non-prototype \
+	-Wno-empty-body -Wno-int-conversion -Wno-int-to-pointer-cast -Wno-main \
+	-Wno-pointer-to-int-cast -Wno-return-type -Wno-unused-label
 
 # Common C compiler warning flags
 #
@@ -86,7 +88,9 @@ CC= cc
 ifeq ($(CC),clang)
 #
 CSILENCE+= -Wno-comma -Wno-format-nonliteral -Wno-missing-variable-declarations \
-	-Wno-pedantic -Wno-poison-system-directories -Wno-strict-prototypes
+	-Wno-pedantic -Wno-poison-system-directories -Wno-strict-prototypes \
+	-Wno-cast-function-type -Wno-float-conversion -Wno-padded \
+	-Wno-unreachable-code
 #
 CWARN+= -Weverything
 #

1984/laman/Makefile

@@ -38,7 +38,8 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-implicit-int
+CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-implicit-int \
+	-Wno-deprecated-non-prototype
 
 # Common C compiler warning flags
 #

1984/mullender/Makefile

@@ -38,7 +38,7 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-main
+CSILENCE= -Wno-main -Wno-deprecated-non-prototype
 
 # Common C compiler warning flags
 #
@@ -83,7 +83,8 @@ CC= cc
 #
 ifeq ($(CC),clang)
 #
-CSILENCE+= -Wno-missing-variable-declarations -Wno-poison-system-directories
+CSILENCE+= -Wno-missing-variable-declarations -Wno-poison-system-directories \
+	-Wno-pedantic -Wno-sign-conversion
 #
 CWARN+= -Weverything
 #