silence compiler warnings for RHEL 9 Linux

We updated ${CSILENCE} Makefile variables for entries in an attempt to
minimize compiler warnings.  This was tested using
gcc version 11.4.1 20230605 (Red Hat 11.4.1-2) (GCC).

TODO: Recheck macOS clang to see if any new warnings have occur
      under macOS clang.

2020/ferguson1/Makefile

@@ -39,8 +39,10 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-unused-value -Wno-implicit-fallthrough -Wno-parentheses \
-	  -Wno-binding-in-condition -Wno-binding-in-condition -Wno-misleading-indentation \
-	  -Wno-unknown-warning-option
+	  -Wno-binding-in-condition -Wno-binding-in-condition \
+	  -Wno-misleading-indentation \Wno-unknown-warning-option \
+	  -Wno-comment -Wno-implicit-function-declaration \
+          -Wno-misleading-indentation -Wno-unused-value
 
 # Common C compiler warning flags
 #
@@ -89,7 +91,8 @@ ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 #
 CSILENCE= -Wno-unused-value -Wno-misleading-indentation -Wno-parentheses \
 	  -Wno-unknown-warning-option -Wno-poison-system-directories \
-	  -Wno-declaration-after-statement -Wno-padded
+	  -Wno-declaration-after-statement -Wno-padded \
+	  -Wno-extra-semi-stmt -Wno-implicit-fallthrough -Wno-unsafe-buffer-usage
 #
 CWARN+= -Weverything
 #