cmd/go: mention examples in docs for -test.run

Missed in my last round. These things sure appear
in a lot of places.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5699096

src/cmd/go/doc.go

@@ -565,7 +565,8 @@ directory containing the package sources, has its own flags:
 	    Verbose output: log all tests as they are run.
 
 	-test.run pattern
-	    Run only those tests matching the regular expression.
+	    Run only those tests and examples matching the regular
+	    expression.
 
 	-test.bench pattern
 	    Run benchmarks matching the regular expression.

src/cmd/go/test.go

@@ -93,7 +93,8 @@ directory containing the package sources, has its own flags:
 	    Verbose output: log all tests as they are run.
 
 	-test.run pattern
-	    Run only those tests matching the regular expression.
+	    Run only those tests and examples matching the regular
+	    expression.
 
 	-test.bench pattern
 	    Run benchmarks matching the regular expression.