Lower warnings again to 3 the right thing would be to fix the warnings

which will be done by discussing with upstream I want the m4 code to stay
as close as possible to upstream.

usr.bin/m4/Makefile

@@ -15,6 +15,8 @@ NO_WMISSING_VARIABLE_DECLARATIONS=
 
 SRCS=	eval.c expr.c look.c main.c misc.c gnum4.c trace.c parser.y tokenizer.l
 
+WARNS=	3
+
 tokenizer.o: parser.h
 
 CLEANFILES+=	parser.c parser.h tokenizer.o