Use gorilla/mux for middleware and extend

- Use gorilla/mux for middleware.
- Add Dumper, RequestID, and Logger middlewares.
- Add makeURL helper

vendor/golang.org/x/sys/unix/mksysctl_openbsd.pl

@@ -32,6 +32,7 @@ my @headers = qw (
 	sys/sem.h
 	sys/shm.h
 	sys/vmmeter.h
+	uvm/uvmexp.h
 	uvm/uvm_param.h
 	uvm/uvm_swap_encrypt.h
 	ddb/db_var.h
@@ -240,7 +241,7 @@ foreach my $header (@headers) {
 
 print <<EOF;
 // mksysctl_openbsd.pl
-// MACHINE GENERATED BY THE ABOVE COMMAND; DO NOT EDIT
+// Code generated by the command above; DO NOT EDIT.
 
 // +build $ENV{'GOARCH'},$ENV{'GOOS'}