CONTRIB: make_srpm.sh can prepare SRPM with patches
    
    Creating SRPM with patches is useful for some static analysers, which can do
    two builds. The first time without patches and the second with patches.
    
    Bash function add_patches is inspired by file rpm/add_patches.sh from project\
    389-ds-base.
       commit 2a92a6cccd1002f4fe976ee7a5b79d779b009f87
       Author: Mark Reynolds
    Thanks.
    
    Resolves:
    https://fedorahosted.org/sssd/ticket/2149
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>