Closes #546

- set the correct stream_id for pushed streams
- init maxdownload and size properly

give the new stream the old one's stream_weight internally to avoid
sending a PRIORITY frame unless asked for it

Fixes warnings 78c25c85 added.

IoctlSocket() apparently wants a pointer to a long, passed as a char *
in its third parameter. This bug was introduced already back in commit
c5fdeef4 from October 1 2001!

Bug: http://curl.haxx.se/mail/lib-2015-11/0088.html
Reported-by: Norbert Kett

Reported-by: Mohammad AlSaleh

Commit f3bae6ed added the URL index to the password prompt when using
--next. Unfortunately, because the size_t specifier (%zu) is not
supported by all sprintf() implementations we use the curl_off_t format
specifier instead. The display of an incorrect value arises on platforms
where size_t and curl_off_t are of a different size.

The RTSP code path didn't skip adding the if-modified-since for certain
RTSP code paths, even if CURLOPT_TIMECONDITION was set to
CURL_TIMECOND_NONE.

Also, an unknown non-zero CURLOPT_TIMECONDITION value no longer equals
CURL_TIMECOND_IFMODSINCE.

Bug: http://stackoverflow.com/questions/33903982/curl-timecond-none-doesnt-work-how-to-remove-if-modified-since-header

... and add a generic explanation for them instead. Each example file
should contain its own description these days.

Fixes #534
Closes #537

It would previously be skipped if an existing error was returned, but
would lead to a previous value being left there and later used.
CURLINFO_TOTAL_TIME for example.

Still it avoids that final progress update if we reached DONE as the
result of a callback abort to avoid another callback to be called after
an abort-by-callback.

Reported-by: Lukas Ruzicka

Closes #538

... to also mention the specific options used.

This reverts commit 64e959ff.

Feedback-by: Dan Fandrich
URL: http://curl.haxx.se/mail/lib-2015-11/0062.html

Refer to _HEADERDATA not _WRITEDATA.

Reported-by: Michał Piechowski

smb.c:134:3: warning: conversion to 'short unsigned int' from 'int' may
             alter its value
smb.c:146:42: warning: conversion to 'unsigned int' from 'long long
              unsigned int' may alter its value
smb.c:146:65: warning: conversion to 'unsigned int' from 'long long
              unsigned int' may alter its value

Regression from commit 7a8e861a as highlighted in the msys autobuilds.

pop3-multi.c:96:5: warning: implicit declaration of function 'memset'
imap-multi.c:96:5: warning: implicit declaration of function 'memset'
http2-download.c:226:5: warning: implicit declaration of function 'memset'
http2-upload.c:290:5: warning: implicit declaration of function 'memset'
http2-upload.c:290:5: warning: implicit declaration of function 'memset'

test845 not present in tests/data/Makefile.inc

Moved some ideas from "next major" to just ordinary ideas since we can
always add new things while keeping the old without doing a "next
major".

Add error-checking to 'cd' in a few cases where omitting the checks
might result in an infinite loop.

Closes #535