warning: comparison between signed and unsigned integer expressions

Don't wait for the next callback call (usually 1 second) before
continuing with protocol specific connection initialization.

This function was modified in nghttp2 git commit a1c3f89c72e51

Otherwise, the FTP protocol would unnecessarily hang 60 seconds if
aborted in the CURLOPT_HEADERFUNCTION callback.

Reported by: Tomas Mlcoch
Bug: https://bugzilla.redhat.com/1005686

Make sure that the custom struct fields are only used by code that
doesn't use a struct defintion from the outside.

Attempts to fix the problem introduced in 3dc6fc42

Otherwise the connection can get stuck during various phases, waiting
for new data on the socket using select() etc., but it will never be
received as the data has already been read into SSL library.

The transfer size would be calculated incorrectly if the email contained
within the FETCH response, had been partially received by the pingpong
layer. As such the following, example output, would be seen if the
amount remaining was smaller than the amount received:

* Excess found in a non pipelined read: excess = 1394, size = 262,
  maxdownload = 262, bytecount = 1374
* transfer closed with -1112 bytes remaining to read

Bug: http://curl.haxx.se/mail/lib-2013-08/0170.html
Reported-by: John Dunn

...from commits 28427b40 and e8313697.

Renamed SUPPORTAUTH to AUTH and added support for specifying a list of
supported SASL mechanisms to return to the client.

Additionally added the directive to the FILEFORMAT document.

Renamed SUPPORTCAPA to CAPA and added support for specifying a list of
supported capabilities to return to the client.

Additionally added the directive to the FILEFORMAT document.

The message numbers given in the LIST response are an index into the
list, which are only valid for the current session, rather than being a
unique message identifier. An index would only be missing from the LIST
response if a DELE command had been issued within the same session and
had not been committed by the end of session QUIT command. Once
committed the POP3 server will regenerate the message numbers in the
next session to be contiguous again. As such our LIST response should
list message numbers contiguously until we support a DELE command in the
same session.

Should a POP3 user require the unique message ID for any or all
messages then they should use the extended UIDL command. This command
will be supported by the test ftpserver in an upcoming commit.

In preparation for additional POP3 tests, re-ordered the command
function defintions to be sorted alphabetically.

Fixed incorrect indentation used in both the RETR_pop3 and LIST_pop3
functions which was 5 and 9 characters rather than 4 and 8.

Detected by test 1132

When building the code using LLVM Clang without NGHTTP2, I was getting
this warning:
../lib/http.h:155:1: warning: empty struct is a GNU extension [-Wgnu]
Placing a dummy variable into the data structure silenced the warning.

Since it now actually says if 1.1 or a later version should be used.

The compiler test used a variable before it was assigned when it tried
to see how it acts on a mismatching prototype, which could cause a false
positive.

Recent OpenSSL uses user interface abstraction to negotiate access to
private keys in the cryprographical engines. An OpenSSL application is
expected to implement the user interface. Otherwise a default one
provided by OpenSSL (interactive standard I/O) will be used and the
aplication will have no way how to pass a password to the engine.

Longer-desc: http://curl.haxx.se/mail/lib-2013-08/0265.html