Step 1 of the Big Error Shift: make os.Error an interface and replace *os.Errors with os.Errors.

lib/template updated to use new setup; its clients also updated.

Step 2 will make os's error support internally much cleaner.

R=rsc
OCL=27586
CL=27586

src/lib/net/parse.go

@@ -55,7 +55,7 @@ func (f *file) readLine() (s string, ok bool) {
 	return
 }
 
-func open(name string) (*file, *os.Error) {
+func open(name string) (*file, os.Error) {
 	fd, err := os.Open(name, os.O_RDONLY, 0);
 	if err != nil {
 		return nil, err;