libgo: update to Go 1.8 release candidate 1

Compiler changes:
  * Change map assignment to use mapassign and assign value directly.
  * Change string iteration to use decoderune, faster for ASCII strings.
  * Change makeslice to take int, and use makeslice64 for larger values.
  * Add new noverflow field to hmap struct used for maps.

Unresolved problems, to be fixed later:
  * Commented out test in go/types/sizes_test.go that doesn't compile.
  * Commented out reflect.TestStructOf test for padding after zero-sized field.

Change-Id: Ifdae97d110fa90944361c238ef07c7b23b1313e2
Reviewed-on: https://go-review.googlesource.com/35231
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/match.sh b/libgo/match.sh
index 23db194..94bcbc8 100755
--- a/libgo/match.sh
+++ b/libgo/match.sh
@@ -151,18 +151,18 @@
 		    fi
 		    match=false
 		    ;;
-		$goos | $goarch | $cgotag | $cmdlinetag)
+		$goos | $goarch | $cgotag | $cmdlinetag | "gccgo")
 		    match=true
 		    ;;
-		"!"$goos | "!"$goarch | "!"$cgotag | "!"$cmdlinetag)
+		"!"$goos | "!"$goarch | "!"$cgotag | "!"$cmdlinetag | "!gccgo")
 		    ;;
 		*,*)
 		    cmatch=true
 		    for ctag in `echo $tag | sed -e 's/,/ /g'`; do
 			case $ctag in
-			    $goos | $goarch | $cgotag | $cmdlinetag)
+			    $goos | $goarch | $cgotag | $cmdlinetag | "gccgo")
 				;;
-			    "!"$goos | "!"$goarch | "!"$cgotag | "!"$cmdlinetag)
+			    "!"$goos | "!"$goarch | "!"$cgotag | "!"$cmdlinetag | "!gccgo")
 				cmatch=false
 				;;
 			    "!"*)