Do not try to check min_perl_version during prereq registration

[autarch]

The call to $self->min_perl_version in the default sub for eumm_version would
be unlikely to get something correct. This is because eumm_version ends up
being called during prereq registration. That means that whatever plugin might
set a perl version prereq may not have run yet.

The symptom of this is you end up losing the min_perl_version bits in the
generated Makefile.PL, because min_perl_version is called too early and ends
up being set to an empty string.

Specifically, I saw this with a number of distro where I have a line like "use
5.0100" in the code and I'm using AutoPrereqs.

[autarch]

I note that this change means that this plugin will always end up setting an EUMM prereq if there are multiple authors. If this is really a big problem I think it might be better to just do what the core dzil MakeMaker plugin does and join the authors together as a string.

[karenetheridge]

This sounds like a simple plugin ordering issue. Your MakeMaker should come after any other prereq source plugin (e.g. MinimumPerl, AutoPrereqs) and then eumm_version will be correct.

The issue of prereqs being needed by MakeMaker is exactly why Makefile.PL content is generated in its own phase, InstallerTool, instead of in the FileMunger phase -- because FileMunger comes before PrereqSource, and InstallerTool comes after.

[autarch]

This seems like an awfully fragile solution. Saying "run this plugin" last doesn't scale very well. At the very least, this could use some documentation.