This patch add a library for client side lookups for a SID or with a
SID through the calls:
- sss_nss_getsidbyname
- sss_nss_getsidbyid
- sss_nss_getnamebysid
- sss_nss_getidbysid
The library is called libsss_nss_idmap and the contributed spec file
will create two new packages libsss_nss_idmap and
libsss_nss_idmap-devel.

https://fedorahosted.org/sssd/ticket/1889

Fixes two minor coverity issues.

Adding missing dependencies for linker. Missing dependency was
introduced by commit 22d381367c27910fe82f476a76b9f4ede555e35a
in changed file src/sss_client/nss_mc_common.c

All function declaration for io.c was moved from util.h to separate file io.h,

https://fedorahosted.org/sssd/ticket/1838

Header file "providers.h" is not included in any other
file and function "dp_process_init" declared in this header file
has no implementation.

Header file protos.h is not also included in any other file and even
hole content is commented out.

Functions open_cloexec and openat_cloexec were renamed with prefix
"sss_" and moved to separete file. Replacing duplicated code of
function sss_open_cloexec everywhere in the source code.

https://fedorahosted.org/sssd/ticket/1794

krb5 1.11 adds support for a new method for responding to
structured data queries. This method, called the responder,
provides an alternative to the prompter interface.

This patch adds support for this method. It takes the password
and provides it via a responder instead of the prompter. In the
case of OTP authentication, it also disables the caching of
credentials (since the credentials are one-time only).

https://fedorahosted.org/sssd/ticket/1819

This reverts commit 30c76633788c498b7d34e7e5944a3d36f26ec2db.