silence most warnings under macOS

For macOS Apple clang version 15.0.0 (clang-1500.3.9.4)
compiler, we have silenced the warnings that can be silenced.

We also updated `.gitignore` for `2014/maffiodo2` and `1995/vanschnitz`.

2005/jetro/Makefile

@@ -86,7 +86,7 @@ ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 CSILENCE+= -Wno-cast-align -Wno-comma -Wno-double-promotion -Wno-missing-prototypes \
 	-Wno-missing-variable-declarations -Wno-padded \
 	-Wno-poison-system-directories -Wno-shadow -Wno-shorten-64-to-32 \
-	-Wno-unused-macros
+	-Wno-unused-macros -Wno-documentation-unknown-command
 #
 CWARN+= -Weverything
 #

2005/toledo/Makefile

@@ -39,7 +39,7 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-bitwise-op-parentheses -Wno-error -Wno-implicit-function-declaration \
-	-Wno-parentheses -Wno-int-conversion -Wno-unsequenced
+	-Wno-parentheses -Wno-int-conversion -Wno-unsequenced -Wno-return-type
 
 # Common C compiler warning flags
 #
@@ -85,7 +85,8 @@ CC= cc
 ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 #
 CSILENCE+= -Wno-float-conversion -Wno-format-nonliteral -Wno-implicit-int-conversion \
-	-Wno-missing-variable-declarations -Wno-poison-system-directories
+	-Wno-missing-variable-declarations -Wno-poison-system-directories \
+	-Wno-missing-prototypes
 #
 CWARN+= -Weverything
 #