Having files named endian.[c|h] seemed to cause issues under Linux so
renamed them both to have the curl_ prefix in the filenames.

lib1900.c:182: (style) Array index 'handlenum' is used before limits
               check

Bug: https://github.com/bagder/curl/pull/133

To allow the little endian functions, currently used in two of the NTLM
source files, to be used by other modules such as the SMB module.

Prefer void for unused parameters, rather than assigning an argument to
itself as a) unintelligent compilers won't optimize it out, b) it can't
be used for const parameters, c) it will cause compilation warnings for
clang with -Wself-assign and d) is inconsistent with other areas of the
curl source code.

smb.c:586: warning: conversion to 'short unsigned int' from 'int' may
           alter its value

Use the connection's upload buffer instead of allocating our own send
buffer.

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.