godoc: remove the last of the global variables, unexport Server

The exported Server becomes handlerServer, and part of Presentation
now.  Presentation is also now an http.Handler with its own
internal mux (a detail, which might go away).

main.go becomes ever simpler.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/11505043
diff --git a/godoc/godoc.go b/godoc/godoc.go
index ee55355..0e0bf71 100644
--- a/godoc/godoc.go
+++ b/godoc/godoc.go
@@ -29,12 +29,9 @@
 	"unicode/utf8"
 )
 
-// Verbose controls logging verbosity.
-var Verbose = false
-
 // Fake relative package path for built-ins. Documentation for all globals
 // (not just exported ones) will be shown for packages in this directory.
-const BuiltinPkgPath = "builtin"
+const builtinPkgPath = "builtin"
 
 // FuncMap defines template functions used in godoc templates.
 //
@@ -232,7 +229,7 @@
 	// because of the irregular mapping under goroot
 	// we need to correct certain relative paths
 	relpath = strings.TrimPrefix(relpath, "src/pkg/")
-	return PkgHandler.pattern[1:] + relpath // remove trailing '/' for relative URL
+	return "pkg/" + relpath // remove trailing '/' for relative URL
 }
 
 // n must be an ast.Node or a *doc.Note