Moving headers used by both server and client to special folder
    
    These are the header files which are used by both client and server:
    src/util/io.h
    src/util/murmurhash3.h
    src/util/util_safealign.h
    
    This patch is about moving these header files to special folder
    (src/shared). It will be easier to identify these headers when looking
    for them in the src tree.
    util_safalign.h is renamed as safalign.h because util_ namespace is
    appropriate when this file belonged to the util's folder which is no
    longer the case.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/1898
    
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>