Added more information to "file already loaded" warning.
Added more information to "file already loaded" warning.

Also changed it to zend_error() so it is more easily suppressed.

google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf