ExtUtils::ParseXS: min perl 5.6.1 => 5.8.3

Increase the minimum required perl release for ExtUtils::ParseXS from
perl-5.6.1 to perl-5.8.3.

The next commit will add 'use fields', which requires at least 5.8.0.
But also, since 2013 the ExtUtils::ParseXS module has had this line:

    use Exporter 'import';

which is only supported in 5.8.3 onwards. Nobody has complained about
this in the last 11 years, so it doesn't look like we need to support an
older perl than that.

Author: iabyn

dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS.pm

@@ -45,7 +45,10 @@ use strict;
 # ones generated when building the perl distribution), to make sure that
 # the only the changes to have appeared are ones which you expected.
 
-use 5.006001;
+# 5.8.0 is required for "use fields"
+# 5.8.3 is required for "use Exporter 'import'"
+use 5.008003;
+
 use Cwd;
 use Config;
 use Exporter 'import';