src/pkg: make package doc comments consistently start with "Package foo".

R=rsc
CC=golang-dev
https://golang.org/cl/4442064
diff --git a/src/pkg/unsafe/unsafe.go b/src/pkg/unsafe/unsafe.go
index 3cd4cff..8507bed 100644
--- a/src/pkg/unsafe/unsafe.go
+++ b/src/pkg/unsafe/unsafe.go
@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 /*
-	The unsafe package contains operations that step around the type safety of Go programs.
+	Package unsafe contains operations that step around the type safety of Go programs.
 */
 package unsafe