Check the NPN result before preparing an HTTP request and switch into
HTTP/2.0 mode if necessary. This is a work in progress, the actual code
to prepare and send the request using nghttp2 is still missing from
Curl_http2_send_request().

To better reflect its purpose

NPN is what is available in the wild today to negotiate SPDY or HTTP/2.0
connections. It is expected to be replaced by ALPN in the future. If
HTTP/2.0 is negotiated, this is indicated for the entire connection and
http.c is expected to initialize itself for HTTP/2.0 instead of
HTTP/1.1.

see:
http://technotes.googlecode.com/git/nextprotoneg.html
http://tools.ietf.org/html/draft-ietf-tls-applayerprotoneg-04

This makes it easier to trace what's happening.

the number of elements in the 'nghttp2_session_callbacks' structure is
now reduced by 2 in version 0.3.0 (I'm not sure when the change
happened, but checking for ver 0.3.0 work for me).

Something is wrong in 'userp' for the HTTP2 recv_callback().  The
session is created using bogus user-data; '&conn' and not 'conn'.

I noticed this since the socket-value in Curl_read_plain() was set to a
impossible high value.

Fixed two compiler nits

...until the function is successful when it returns them in the out
parameters.

Added conversion functions write32_le() and write64_le() to ensure the
NTLMv2 timestamp is always written in little-endian.

It is not provided by NSS public headers.

Bug: https://bugzilla.redhat.com/1058776

... that the user does not ask for

hostcache_timestamp_remove() should remove old *unused* entries from the
host cache, but it never checked whether the entry was actually in
use. This complements commit 030a2b8c.

Bug: http://curl.haxx.se/bug/view.cgi?id=1327

tftp_done() can get called with its TFTP state pointer still being NULL
on an early time-out, which caused a segfault when dereferenced.

Reported-by: Glenn Sheridan
Bug: http://curl.haxx.se/mail/lib-2014-01/0246.html

Incorrect password if use backspace while entered the password.

Regression from f7bfdbab

The '?:' operator has lower priority than the '-' operator

Since the previous complex select function with initial support for
non-socket file descriptors, did not actually work correctly for
Console handles, this change simplifies the whole procedure by using
an internal waiting thread for the stdin console handle.

The previous implementation made it continuously trigger for the stdin
handle if it was being redirected to a parent process instead of
an actual Console input window.

This approach supports actual Console input handles as well as
anonymous Pipe handles which are used during input redirection.

It depends on the fact that ReadFile supports trying to read zero bytes
which makes it wait for the handle to become ready for reading.