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.

1989/robison/Makefile

@@ -39,7 +39,8 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-unused-parameter -Wno-deprecated-non-prototype -Wno-format-extra-args \
-        -Wno-int-to-pointer-cast -Wno-strict-prototypes -Wno-implicit-int
+          -Wno-int-to-pointer-cast -Wno-strict-prototypes -Wno-implicit-int \
+	  -Wno-return-type -Wno-uninitialized -Wno-unused-value
 
 # Common C compiler warning flags
 #
@@ -89,7 +90,8 @@ CC= cc
 ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 #
 CSILENCE+= -Wno-missing-prototypes -Wno-poison-system-directories \
-	-Wno-strict-prototypes -Wno-bad-function-cast -Wno-missing-variable-declarations
+	   -Wno-strict-prototypes -Wno-bad-function-cast -Wno-missing-variable-declarations \
+	   -Wno-unsafe-buffer-usage
 #
 CWARN+= -Weverything
 #