perl-module: Tolerate minor PSPP version number differences.

The PSPP autobuilder that I'm working on appends a build number to the PSPP
version number, e.g. "0.7.2-build40".  The Perl module has two problems
with this:

  1. Perl won't parse version numbers that contain anything other than
     digits and periods, so "-build" causes an error.  So this commit
     drops everything from the hyphen onward from the PSPP version number
     passed along to Perl.

  2. The Perl module itself does a string comparison operation between the
     number it expects and the number that PSPP reports.  When we drop
     the hyphen onward, the comparison fails.  So this commit also relaxes
     the comparison to one that does pass.