core.buffer: fix readline not to use event_readline which strips the newlines; also, accept 'size' argument for compatibility with WebOb. Patch by Ralf Schmitt.

This improves compatibility with WebOb.

avoid Python name lookups when accessing EV_* constants from Cython code. Patch by Daniele Varrazzo.

- patch_socket() does not patch ssl so it won't work on https urls (even though
  this example does not use https, someone might get an idea that it does)