Update 0.55 to 0.57
-------------------
0.57    2015-04-17 15:20 UTC
        + Chg : The new environment variable to enable thread tests on older
                perls is PERL_FORCE_TEST_THREADS. Note that this variable
                should only be turned on by authors.
        + Fix : Segfaults when the module is loaded by several threads (or
                Windows emulated processes) ran in parallel.
        + Fix : Segfaults when the module is loaded in a thread, which spawns
                itself a new thread, and that child thread outlives its parent.
        + Fix : Small memory leaks of structures required for thread safety.
        + Fix : Update the Windows ActivePerl + gcc 3.4 workaround for
                ExtUtils::MakeMaker 7.04. Thanks Christian Walde for reporting
                and feedback on this issue.
        + Tst : The global destruction test will now be exercised on any perl
                that has DEBUGGING set.
        + Tst : Optional capturing tests in t/17-ctl.t that were only run when
                Capture::Tiny was present were converted to an IPC::Open3
                based helper and will now be run everywhere.

0.56    2015-03-11 15:15 UTC
        + Fix : [RT #101410] : Install fails in blead
                Even though the change that caused this error was reverted from
                blead, lvalue uses of ERRSV have been removed from this module
                so that there will be no breakage when this change is possibly
                reintroduced in the following months.
                Thanks Dave Rolsky for reporting.
        + Tst : $ENV{$Config{ldlibpthname}} is now preserved on all platforms,
                which will address failures of t/17-ctl.t with unusual
                compilers (like icc) that link all their compiled objects to
                their own libraries.
        + Tst : The global destruction test is now only run on perl 5.13.4 and
                higher, and only if either Perl::Destruct::Level is installed
                or PERL_DESTRUCT_LEVEL is set and the perl is a debugging perl.
                This will solve rare crashes of t/15-self.t on perl 5.13.3 and
                older.


(mef)