pop3: Removed unnecessary transfer cancellation

Following commit e450f66a02d8 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.
test509: libcurl initialization with memory callbacks and actual usage
tool_main.c: remove redundant vms_show storage-class specifier

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)
Multiple pipelines and limiting the number of connections.

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.
pipelining: Remove dead code.
Makefile.vc6: add missing files
curl_memory.h: introduce CURLX_NO_MEMORY_CALLBACKS usage possibility

This commit alone does not fix anything nor modifies existing
interfaces or behaviors, although it is a prerequisite for other
fixes.
ftpserver.pl: Added EXAMINE_imap() for IMAP EXAMINE commands

Used hard coded data from RFC-3501 section 6.3.2.
HTTP proxy: insert slash in URL if missing

curl has been accepting URLs using slightly wrong syntax for a long
time, such as when completely missing as slash "http://example.org" or
missing a slash when a query part is given
"http://example.org?q=foobar".

curl would translate these into a legitimate HTTP request to servers,
although as was shown in bug #1206 it was not adjusted properly in the
cases where a HTTP proxy was used.

Test 1213 and 1214 were added to the test suite to verify this fix.

The test HTTP server was adjusted to allow us to specify test number in
the host name only without using any slashes in a given URL.

Bug: http://curl.haxx.se/bug/view.cgi?id=1206
Reported by: ScottJi
imap-tests: Added test808 for custom EXAMINE command
tests: add #96 #558 and #1330

These verfy that the 'memory tracking' subsystem is actually doing its
job when using curl tool (#96), a test in libtest (#558) and also a unit
test (#1330), in order to prevent regressions in this functionallity.
unit1330.c: fix date
imap-tests: Corrected copy/paste error in test808 reply data
TODO: Added section 10.2 Initial response to POP3 to do list
tests: 96, 558, 1330: strip build subdirectory dependent leading path
TODO: Corrected typo on section 10.2 heading
TODO: Added graceful base64 decoding failure to SMTP and POP3
TODO: Added IMAP section and removed unused Other protocols section
TODO: Corrected typo in TOC
FEATURES: Expanded the supported enhanced IMAP command list