perl-module: Additional fixes for Perl version number on PSPP autobuilder.

Commit 30f21302 "perl-module: Tolerate minor PSPP version number
differences" tried to improve the behavior of the PSPP Perl module when
the PSPP version number includes a suffix such as -build40.  But it didn't
entirely work, since it overlooked some uses of $(VERSION) in
perl-module/automake.mk.  This commit fixes those too.