[dev] Bug in MIME_Structure::parseMIMEHeaders

[Mike Cochrane]

There seems to be bug in MIME_Structure::parseMIMEHeaders when a header is set
without a space after the ':'.

In RFC2822 is says:
    2.2. Header Fields

       Header fields are lines composed of a field name, followed by a colon
      (":"), followed by a field body, and terminated by CRLF.

It doesn't mention anything about requiring a space. If the space is omitted the
code fails to pick up this header. 

If anyone needs a message bounced their way to test this i have heaps.

- Mike :-)