Rename SAFEALIGN macros.
    
    https://fedorahosted.org/sssd/ticket/1772
    
    SAFEALIGN macros have been renamed in this patch to
    make it easy to pick the right macro when data is copied
    from byte buffer to a variable or vice versa.
    
    The renamed macros are placed in new header file to
    avoid code duplication (the old ones were defined in
    two files, one for the client code and one for the rest
    of sssd).