When we know the compiler is GCC, always add the -Wall and

-Wstrict-prototypes options.  This will make it a lot easier to keep
warnings under control in the first place in the future.

There is one known warning at this time, caught by the -Wstrict-prototypes
option.  In Modules/main.c, the declaration of getopt() without parameters
gets a complaint (rightly) that it is not a proper prototype.  The lack of
a complete prototype information should be corrected when the right
portability conditions have been identified.

Approved by the Guido.

configure.in

@@ -308,8 +308,8 @@ then
 	case $GCC in
 	yes)
 		case $ac_cv_prog_cc_g in
-		yes)	OPT="-g -O2";;
-		*)	OPT="-O2";;
+		yes)	OPT="-g -O2 -Wall -Wstrict-prototypes";;
+		*)	OPT="-O2 -Wall -Wstrict-prototypes";;
 		esac
 		;;
 	*)	OPT="-O";;