This commit alone does not fix anything nor modifies existing
interfaces or behaviors, although it is a prerequisite for other
fixes.

Introducing a number of options to the multi interface that
allows for multiple pipelines to the same host, in order to
optimize the balance between the penalty for opening new
connections and the potential pipelining latency.

Two new options for limiting the number of connections:

CURLMOPT_MAX_HOST_CONNECTIONS - Limits the number of running connections
to the same host. When adding a handle that exceeds this limit,
that handle will be put in a pending state until another handle is
finished, so we can reuse the connection.

CURLMOPT_MAX_TOTAL_CONNECTIONS - Limits the number of connections in total.
When adding a handle that exceeds this limit,
that handle will be put in a pending state until another handle is
finished. The free connection will then be reused, if possible, or
closed if the pending handle can't reuse it.

Several new options for pipelining:

CURLMOPT_MAX_PIPELINE_LENGTH - Limits the pipeling length. If a
pipeline is "full" when a connection is to be reused, a new connection
will be opened if the CURLMOPT_MAX_xxx_CONNECTIONS limits allow it.
If not, the handle will be put in a pending state until a connection is
ready (either free or a pipe got shorter).

CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE - A pipelined connection will not
be reused if it is currently processing a transfer with a content
length that is larger than this.

CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE - A pipelined connection will not
be reused if it is currently processing a chunk larger than this.

CURLMOPT_PIPELINING_SITE_BL - A blacklist of hosts that don't allow
pipelining.

CURLMOPT_PIPELINING_SERVER_BL - A blacklist of server types that don't allow
pipelining.

See the curl_multi_setopt() man page for details.

vms_show 'extern' storage-class specifier removed from tool_main.c due to...

- Advice from Tor Arntsen: http://curl.haxx.se/mail/lib-2013-03/0164.html

- HP OpenVMS docs stating that 'Extern is the default storage class for
  variables declared outside a function.'
  http://h71000.www7.hp.com/commercial/c/docs/dec_c_help_5.html
  (Storage_Classes section)

Following commit e450f66a and the changes in the multi interface
being used internally, from 7.29.0, the transfer cancellation in
pop3_dophase_done() is no longer required.

Added missing slash in cc_full_list.
Removed unwanted extra quotes inside symbol tool_main
for non-VAX architectures that triggered link failure.
Replaced curl_sys_inc with sys_inc.

An extern submits a psect and a global reference to the linker to point
to it. Using "extern int vms_show = 0" also creates a globaldef.

The use of the extern by itself does declare a psect but does not declare
a globalsymbol. It does declare a globalref. But the linker needs one and
only one globaldef or there is an error.

Don't initiate a transfer when using --ftp-list.

The flag can be used in pycurl-based applications where using the multi
interface would not be acceptable because of the performance lost caused
by implementing the select() loop in python.

Bug: http://curl.haxx.se/bug/view.cgi?id=1168
Downstream Bug: https://bugzilla.redhat.com/919127

No API change involved.

Info: http://curl.haxx.se/mail/lib-2013-02/0234.html

since mails sent are supposed to have CRLF line endings I added them and
now the data size after (\Seen) matches again properly

Corrected a couple of tab characters between test702 and test703, and
between test900 and test901 which should be spaces.

Added one test for a request with matching UIDVALIDITY and one which is
a mismatched request that will fail.

Any IMAP parameter can come in escaped and in double quotes. Added a
simple function to unquote the command parameters and applied it to
the IMAP command handlers.

The whole of FETCH_imap() had one extra space of indentation, whilst
APPEND_imap() used indentation of 2 instead of 4 in places.

The majority of lines, that specify a test file for inclusion, end with
a tab character before the slash whilst some end with a space. Corrected
those that end with a space to end with a tab character as well.

Finished segregating the email protocol tests, into their own protocol
based ranges, in preparation of adding more e-mail related tests to the
test suite.

Continued segregating the email protocol tests, into their own protocol
based ranges, in preparation of adding more e-mail related tests to the
test suite.

Continued segregating the email protocol tests, into their own protocol
based ranges, in preparation of adding more e-mail related tests to the
test suite.

Started segregating the email protocol tests, into their own protocol
based ranges, in preparation of adding more e-mail related tests to the
test suite.

Patch by: Myk Taylor

... hopefully this will also make clang-analyzer stop warning on
potentional NULL dereferences (which were false positives anyway).

When Curl_do() returns failure, the connection pointer could be NULL so
the code path following needs to that that into account.

Bug: http://curl.haxx.se/mail/lib-2013-03/0062.html
Reported by: Eric Hu