[poppler] Changes to 'unique_ptr'

[Carlos Garcia Campos]

New branch 'unique_ptr' available with the following commits:
commit acd903c5b4dacd5f844bc9240ca745671f74cffc
Author: Carlos Garcia Campos <carlosgc at gnome.org>
Date:   Sun May 21 14:14:19 2017 +0200

    annots: Use std::unique_ptr instead of new/delete

commit 4a4393c06e81aa52701aa925346115b4eea694d7
Author: Carlos Garcia Campos <carlosgc at gnome.org>
Date:   Sun May 21 14:13:30 2017 +0200

    Add std::make_unique implementation
    
    It's not available in C++11, it was added in C++14.