Moved imap_select() and imap_fetch() to be grouped with the other
perform functions.

Exchanged the position of these states in the switch statements to
match the state enum, execution and function order.

Tidy up of comments before next round of imap changes.

Corrected the comparison type in addition to commit 1dac29fa.

URL examples that included the UID weren't technically correct although
would pass the curl parser.

I also added --with-darwinssl to the list of SSL options in configure.

From a maintenance point of view the code reads better to view tagged
responses, then untagged followed by continuation responses.

Additionally, this matches the order of responses in POP3.

Enhanced the parsing to only allow continuation responses in some
states.

Enhanced the parsing of tagged responses which must start with "OK",
"NO" or "BAD"

Corrected layout issues with the POP3 and IMAP URL examples introduced
in commit cb3ae689.

Updated the POP3 sub-section to refer to message ID rather than mailbox.

Added an IMAP sub-section with example URLs depicting the specification
of mailbox, uid and section.

Updated the mailbox variable to correctly reflect it's purpose. The
name mailbox was a leftover from when IMAP and POP3 support was
initially added to curl.

Updated the FETCH command to send the UID and SECTION parsed from the
URL. By default the BODY specifier doesn't include a section, BODY[] is
now sent whereas BODY[TEXT] was previously sent. In my opinion
retrieving just the message text is rarely useful when dealing with
emails, as the headers are required for example, so that functionality
is not retained. In can however be simulated by adding SECTION=TEXT to
the URL.

Also updated test801 and test1321 due to the BODY change.

Removed user and passwd from the SMTP struct as these cannot be set on
a per-request basis and are leftover from legacy FTP code.

Changed some comments still using FTP terminology.

Moved the rcpt variable from the per-connection struct smtp_conn to the
new per-request struct and fixed references accordingly.

Created a new SMTP structure and changed the type of the smtp proto
variable in connectdata from FTP* to SMTP*.

error: declaration of 'pop3' shadows a previous local

Updated the imap_parse_url_path() function to parse uidvalidity, uid and
section parameters based on RFC-5092.

Added imap_is_bchar() for testing if a given character is a valid bchar
or not.

Added uidvalidity, uid and section variables to the per-request IMAP
structure in preparation for upcoming URL parsing.

Removed user and passwd from the POP3 struct as these cannot be set on
a per-request basis and are leftover from legacy FTP code.

Changed some comments still using FTP terminology.

Moved the mailbox and custom request variables from the per-connection
struct pop3_conn to the new per-request struct and fixed references
accordingly.

Created a new POP3 structure and changed the type of the pop3 proto
variable in connectdata from FTP* to POP*.

Used imap_atom() to escape mailbox names in imap_select().

Moved the ftp transfer structure into pingpong.h so other protocols that
require it don't have to include ftp.h.

Corrected comment for opt_no_body variable to CURLOPT_NOBODY.

Changed some variables and comments still using FTP terminology.

Removed user and passwd from the IMAP struct as these cannot be set on
a per-request basis and are leftover from legacy FTP code.