Updated the naming convention of the login parameters to match those of
other functions.

Tidy up of variable names and comments in setstropt_userpwd() and
parse_login_details().

There is no need to perform separate clearing of data if a NULL option
pointer is passed in. Instead this operation can be performed by simply
not calling parse_login_details() and letting the rest of the code do
the work.

setstropt_userpwd() was calling setstropt() in commit fddb7b44 to
set each of the login details which would duplicate the strings and
subsequently cause a memory leak.

Fix to prevent the options from being displayed when curl requests the
user's password if the following command line is specified:

--user username;options

In addition to parsing the optional login options from the URL, added
support for parsing them from CURLOPT_USERPWD, to allow the following
supported command line:

--user username:password;options

Added bounds checking when searching for the separator characters within
the login string as this string may not be NULL terminated (For example
it is the login part of a URL). We do this in preference to allocating a
new string to copy the login details into which could then be passed to
parse_login_details() for performance reasons.

When cross-compiling we can't scan and detect existing files or paths.

Bug: http://curl.haxx.se/mail/lib-2013-04/0294.html

Relies on CURLOPT_SSL_CTX_FUNCTION, which is OpenSSL specific

signed and unsigned type in conditional expression

Separated the parsing of login details from the processing of them in
parse_url_login() ready for use by setstropt_userpwd().

Re-factored these functions to reflect their new behaviour following the
addition of login options.

Apparently the previous usage didn't work with that implementation,
while this updated version works with at least both Parallel BZIP2
v1.1.8 and regular bzip "Version 1.0.6, 6-Sept-2010".

Standardised the naming of all perform based functions to be in the form
smtp_perform_something().

Curl-config outputs static libraries even when they are disabled in
configure.

This causes problems with the build of pycurl.

Commit c3ea3eb6 introduced some minor cosmetic errors in
curl_mutli_socket_action(3).

These are needed in cases where clock_gettime is used, from librt.

Also note the prohibition on sharing handles across threads.

Updated the coding style, in this function, to be consistant with other
response functions rather then performing a hard return on failure.

Updated the coding style, in this function, to be consistent with other
response functions rather then performing a hard return on failure.

Standardised the naming of all perform based functions to be in the form
pop3_perform_something() following the changes made to IMAP.

Started to apply the same tidy up to the POP3 code as applied to the
IMAP code in the 7.30.0 release.