ISSUE-91: Invoking send() multiple times is undefined

ISSUE-91: Invoking send() multiple times is undefined

http://www.w3.org/2005/06/tracker/webapi/issues/91

Raised by: Anne van Kesteren
On product: XMLHttpRequest

Because invoking send() can't directly change readyState cases like:

  client.open(...)
  client.send()
  client.send()

... are currently undefined. User agents seem to do various things... This and 
some other issues seem to ask for some readyState value of 1.5 or something...