Update to 2.11

Upstream changes:
2.11  2015-08-16 Shlomif
    - Got the distribution to have full POD coverage and check all functions
    for usage.
        - t/check-funcs-ret-value--rt92593.t
        - https://rt.cpan.org/Public/Bug/Display.html?id=92593
        - CPAN Day!

2.10  2015-08-12 Shlomif
    - Throw an exception on invalid input to Math::GMP->new;
        - https://rt.cpan.org/Ticket/Display.html?id=27521
        - Thanks to SISYPHUS for the report.
    - Put RELEASE_TESTING tests under xt instead of t.
        - https://rt.cpan.org/Ticket/Display.html?id=106365
        - Thanks to ilmari for the report and suggested fix.
    - Document and test some functions that were improperly documented or
    not tested.
        - t/check-funcs-ret-value--rt92593.t
        - https://rt.cpan.org/Public/Bug/Display.html?id=92593
        - Still aiming for full POD Coverage.

2.09  2015-07-29 Shlomif
    - Add the binary-left-shift / << operator.
    - Add the binary-right-shift / >> operator.
    - Convert the build system to Dist-Zilla to ease future maintenance.
    - Add a call to Devel::CheckLib for finding the "gmp.h" header.

2.08  2015-07-28 Shlomif
    - Add a link to the version control repository at various places.
    - Get rid of indirect object notation in the code and the examples.
        - It�塜 a sign of Ancient Perl.
    - Overload bool to avoid fallback to intify (Hugo)
        - Fixes RT #101443
            - https://rt.cpan.org/Ticket/Display.html?id=101443
        - Modified patch applied by Shlomif.
    - Add tests from DANAJ for large numbers in some functions.
        - RT #92641
            - https://rt.cpan.org/Ticket/Display.html?id=92641

(wen)