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

When an option's help string contains literal single quotes, those
single quotes would be stripped from the option's description in the
completion output (unless the zsh RC_QUOTES option were set while the
completion function was being sourced, which is not the default).  This
patch makes the completion output contain single quotes where the --help
output does.

Closes #532

Closes https://github.com/bagder/curl/pull/533

The push headers are freed after the push callback has been invoked,
meaning this code should only free the headers if the callback was never
invoked and thus the headers weren't freed at that time.

Reported-by: Davey Shafik

Closes #528

... if there are more than one using the same name

As POP3 final and continuation responses both begin with a + character,
and both the finalcode and contcode variables in SASLprotoc are set as
such, we cannot tell the difference between them when we are expecting
an optional continuation from the server such as the following:

+ something else from the server
+OK final response

Disabled these tests until such a time we can tell the responses apart.

According to RFC7628 a failure message may be sent by the server in a
base64 encoded JSON string as a continuation response.

Currently only implemented for OAUTHBEARER and not XAUTH2.

OAUTHBEARER is now the official "registered" SASL mechanism name for
OAuth 2.0. However, we don't want to drop support for XOAUTH2 as some
servers won't support the new mechanism yet.