Updated XSLoader to CPAN version 0.15

Updated XSLoader to CPAN version 0.15

  [DELTA]

  0.15 - 2011.04.17 - SAPER #PerlQA2011
    - [DIST] CPAN-RT#54456: Set INSTALLDIRS to "site" when installed on
      Perl 5.11+ (thanks to Todd Rinaldo).
    - [DOC] Document a known bug under Perl 5.8.4 and 5.8.5.
    - [TESTS] Fixed tests to pass under Perl 5.8.4 and 5.8.5.

  0.14 - 2011.04.16 - SAPER #PerlQA2011
    - [CODE] Updated from bleadperl:
       - XSLoader::load() with no arguments can use caller to find
         a default package (Nicholas Clark).
       - Avoid defining a full XSLoader::bootstrap_inherit post 5.6,
         as it's not needed (Nicholas Clark).
       - Small optimisation: for the generated XSLoader.pm, avoid a
         runtime lexical which is constant (Nicholas Clark).
    - [TESTS] Updated from bleadperl, solving RT-CPAN #54132, #61332.
    - [TESTS] Fixed tests for old Perls.
    - [TESTS] Added t/00-load.t and t/01-api.t, to provide basic tests
      when the main ones are skipped.