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.

2004/vik2/Makefile

@@ -38,7 +38,8 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-strict-prototypes -Wno-implicit-function-declaration
+CSILENCE= -Wno-strict-prototypes -Wno-implicit-function-declaration \
+	  -Wno-builtin-declaration-mismatch
 
 # Common C compiler warning flags
 #
@@ -83,7 +84,8 @@ CC= cc
 #
 ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 #
-CSILENCE+= -Wno-poison-system-directories -Wno-unused-macros
+CSILENCE+= -Wno-poison-system-directories -Wno-unused-macros \
+	   -Wno-reserved-macro-identifier -Wno-unknown-warning-option
 #
 CWARN+= -Weverything
 #