On Perl 5.17.9, t/apache/read2.t fails because an "uninitialized value"
warning is generated for the buffer being autovivified. This is because
the sv_setpvn() that's meant to vivify the buffer doesn't perform set
magic; the warning is generated by the immediately following SvPV_force().
Patch to fix this from rt.cpan.org #83922. [Zefram]

git-svn-id: https://svn.apache.org/repos/asf/perl/modperl/trunk@1456372 13f79535-47bb-0310-9956-ffa450edef68