Adapt Configure to GCC version 10

backport of 9f4e6307232229875331a55e44e1245b0b91e219

U/compline/ccflags.U

@@ -184,14 +184,14 @@ fi
 case "$hint" in
 default|recommended)
 	case "$gccversion" in
-	1*) dflt="$dflt -fpcc-struct-return" ;;
+	1.*) dflt="$dflt -fpcc-struct-return" ;;
 	esac
 	case "$optimize:$DEBUGGING" in
 	*-g*:old) dflt="$dflt -DDEBUGGING";;
 	esac
 ?X: check for POSIXized ISC
 	case "$gccversion" in
-	2*) if $test -d /etc/conf/kconfig.d &&
+	2.*) if $test -d /etc/conf/kconfig.d &&
 			$contains _POSIX_VERSION $usrinc/sys/unistd.h >/dev/null 2>&1
 		then
 			# Interactive Systems (ISC) POSIX mode.
@@ -205,7 +205,7 @@ default|recommended)
 ?X: greater than 2.8.
 ?X:	--Andy Dougherty  27 Aug 1999
 	case "$gccversion" in
-	1*) ;;
+	1.*) ;;
 	2.[0-8]*) ;;
 	?*)	set strict-aliasing -fno-strict-aliasing
 		eval $checkccflag
@@ -331,7 +331,7 @@ case "$cppflags" in
     ;;
 esac
 case "$gccversion" in
-1*) cppflags="$cppflags -D__GNUC__"
+1.*) cppflags="$cppflags -D__GNUC__"
 esac
 case "$mips_type" in
 '');;

U/modified/Cppsym.U

@@ -316,7 +316,7 @@ fi
 
 : add -D_FORTIFY_SOURCE if feasible and not already there
 case "$gccversion" in
-[456789].*)	case "$optimize$ccflags" in
+[456789].*|[1-9][0-9]*)	case "$optimize$ccflags" in
 	*-O*)	case "$ccflags$cppsymbols" in
 		*_FORTIFY_SOURCE=*) # Don't add it again.
 			echo "You seem to have -D_FORTIFY_SOURCE already, not adding it." >&4

U/perl/gccvers.U

@@ -80,7 +80,7 @@ else
 fi
 $rm -f try try.*
 case "$gccversion" in
-1*) cpp=`./loc gcc-cpp $cpp $pth` ;;
+1.*) cpp=`./loc gcc-cpp $cpp $pth` ;;
 esac
 case "$gccversion" in
 '') gccosandvers='' ;;
@@ -120,7 +120,7 @@ esac
 # gcc 3.* complain about adding -Idirectories that they already know about,
 # so we will take those off from locincpth.
 case "$gccversion" in
-3*)
+3.*)
     echo "main(){}">try.c
     for incdir in $locincpth; do
        warn=`$cc $ccflags -I$incdir -c try.c 2>&1 | \