Including headers in response body will break Metalink XML parser.
If it is included in the file described in Metalink XML, hash check
will fail. Therefore, --include should be ignored if --metalink is
used.

The noprogress and isatty in Configurable are global, in a sense
that they persist in one curl invocation. Currently once one
download writes its response data to tty, they are set to FALSE
and they are not restored on successive downloads.  This change
first backups the current noprogress and isatty, and restores
them when download does not write its data to tty.

In this change, --metalink option no longer takes argument.  If
it is specified, given URIs are processed as Metalink XML file.
If given URIs are remote (e.g., http URI), curl downloads it
first. Regardless URI is local file (e.g., file URI scheme) or
remote, Metalink XML file is not written to local file system and
the received data is fed into Metalink XML parser directly.  This
means with --metalink option, filename related options like -O
and -o are ignored.

Usage examples:

$ curl --metalink http://example.org/foo.metalink

This will download foo.metalink and parse it and then download
the URI described there.

$ curl --metalink file://foo.metalink

This will parse local file foo.metalink and then download the URI
described there.

When creating metalink_checksum from metalink_checksum_t, first
check hex digest is valid for the given hash function.  We do
this check in the order of digest_aliases so that first good
match will be chosen (strongest hash function available).  As a
result, the metalinkfile now only contains at most one
metalink_checksum because other entries are just redundant.

http://curl.haxx.se/mail/archive-2012-06/0028.html

Removed two, not intended to exist, RESOURCE declarations.

Bug: http://curl.haxx.se/bug/view.cgi?id=3535977

And sorted configuration hunks to reflect same internal order
as the one shown in the usage message.

Increase decrypted and encrypted cache buffers using limitted
doubling strategy. More information on the mailinglist:
http://curl.haxx.se/mail/lib-2012-06/0255.html

It updates the two remaining reallocations that have already been there
and fixes the other one to use the same "do we need to increase the
buffer"-condition as the other two.  CURL_SCHANNEL_BUFFER_STEP_SIZE was
renamed to CURL_SCHANNEL_BUFFER_FREE_SIZE since that is actually what it
is now.  Since we don't know how much more data we are going to read
during the handshake, CURL_SCHANNEL_BUFFER_FREE_SIZE is used as the
minimum free space required in the buffer for the next operation.
CURL_SCHANNEL_BUFFER_STEP_SIZE was used for that before, too, but since
we don't have a step size now, the define was renamed.

In schannel_connect_step2() doread should be initialized based
on connssl->connecting_state.

Test definition section parts which needed to include xml-lingo as contents
of that part required that the xml-blurb was written as a single line. Now the
xml-data inside the part can be written multiline making it more readable.

Tested with <client><file> part which is written to disk before <command> runs.

Process extra data buffer before returning from schannel_connect_step2.
Without this change I've seen WinCE hang when schannel_connect_step2
returns and calls Curl_socket_ready.

If the encrypted handshake does not fit in the intial buffer (seen with
large certificate chain), increasing the encrypted data buffer is necessary.

Fixed warning in curl_schannel.c line 1215.

process.h is not present on WinCE

Implemented timeout loop in schannel_send while sending data.  This
is as close as I think we can get to write buffering; I put a big
comment in to explain my thinking.

With some committer adjustments

Replaced calls to swrite with Curl_write_plain and calls to sread
with Curl_read_plain.

With some committer adjustments

Make the Schannel implementation use libcurl's default buffer size
for the initial received encrypted and decrypted data cache buffers.
The implementation still needs to handle more data since more data
might have already been received or decrypted during the handshake
or a read operation which needs to be cached for the next read.

curl_schannel.c - implemented graceful SSL shutdown.  If we fail to
shutdown the connection gracefully, I've seen schannel try to use a
session ID for future connects and the server aborts the connection
during the handshake.

curl_schannel.c - auto certificate validation doesn't seem to work
right on CE.  I added a method to perform the certificate validation
which uses CertGetCertificateChain and manually handles the result.

Added helper methods InitSecBuffer() and InitSecBufferDesc() to make it
easier to set up SecBuffer & SecBufferDesc structs.

Avoid usage of some MS type synonyms to allow compilation with
compiler headers that don't define these, using simpler synonyms.

Coverity actually pointed out flawed logic in the previous call to
Curl_strntoupper() where the code used sizeof() of a pointer to pass in
a size argument. That code still worked since it only needed to
uppercase 4 letters. Still, the entire malloc/uppercase/free sequence
was pointless since the code has already matched the string once in the
condition that starts the block of code.

As spotted by Coverity, va_end() was not used previously. To make it
used I took away a bunch of return statements and made them into
assignments instead.