Moved our Initialize Security Context return attribute definitions to
the SSPI module, as a) these can be used by other SSPI based providers
and b) the ISC required attributes are defined there.

vtls.c:683:43: warning: unused parameter 'data'

sockfilt.c:288: warning: conversion to 'DWORD' from 'size_t' may alter
                its value
sockfilt.c:291: warning: conversion to 'DWORD' from 'size_t' may alter
                its value
sockfilt.c:323: warning: conversion to 'DWORD' from 'size_t' may alter
                its value
sockfilt.c:326: warning: conversion to 'DWORD' from 'size_t' may alter
                its value

lib1509.c:93:18: warning: conversion to 'long int' from 'size_t' may
                 alter its value

lib556.c:90: warning: conversion to 'unsigned int' from 'size_t' may
             alter its value

curl_schannel.h:123: warning: right-hand operand of comma expression
                     has no effect

Some instances of the curlssl_close_all() function were declared with a
void return type whilst others as int. The schannel version returned
CURLE_NOT_BUILT_IN and others simply returned zero, but in all cases the
return code was ignored by the calling function Curl_ssl_close_all().

For the time being and to keep the internal API consistent, changed all
declarations to use a void return type.

To reduce code we might want to consider removing the unimplemented
versions and use a void #define like schannel does.

* Missing initialisation of upload status caused a seg fault
* Missing data termination caused corrupt data to be uploaded
* Data verification should be performed in <upload> element
* Added missing recipient list cleanup

This frees up the 'result' variable for CURLcode based result codes.

...and don't use CURLE_OK in failure/success comparisons.

As this feature has been implemented for 7.40.0.

...as calloc() automatically clears the area of memory with zeros.

...with the exception of the start of block statement curly brackets.

For consistency, as we seem to have a bit of a mixed bag, changed all
instances of ipv4 and ipv6 in comments and documentations to use the
correct case.

...following change in curl --version output.

Use Unix when generically writing about Unix based systems as UNIX is
the trademark and should only be used in a particular product's name.

if2ip.c:119: warning: unused parameter 'remote_scope_id'

...and some minor code style policing in the same function.

Otherwise Curl_ssl_init_certinfo() can fail and set the num_of_certs
member variable to the requested count, which could then be used
incorrectly as libcurl closes down.

The return type for this function was 0 on success and 1 on error. This
was then examined by the calling functions and, in most cases, used to
return CURLE_OUT_OF_MEMORY.

Instead use CURLcode for the return type and return the out of memory
error directly, propagating it up the call stack.

To match the curl --version output.

Merge multiple internal arrays into one, even if some variables
will not not be used. They are all created with the number of
file descriptors as their size.

Also fix possible thread handle leak in CloseHandle-loop.

Improves performance of test cases 574 and 575 by 50%.

A value of zero causes the thread to relinquish the remainder
of its time slice to any other thread of equal priority that is
ready to run. If there are no other threads of equal priority
ready to run, the function returns immediately, and the thread
continues execution.

http://msdn.microsoft.com/library/windows/desktop/ms686307.aspx

In line with the other features listed in the --version output,
capitalise the UNIX socket feature.

The return type of this function is a boolean value, and even uses a
bool internally, so use bool in the function declaration as well as
the variables that store the return value, to avoid any confusion.