Also test the automatic backend choosing
Skip normal executable tests on DOS or Windows platforms
Add backend name to all test descriptions
No more consider boilerplate.t as TODO
Add some meta information to Build.PL
Should now work properly on Windows, DOS, etc., too

Run::Parts::Perl specifically accepts suffixes if running on Windows.

Also adds a specific test to test this new feature -- which runs only
on DOS-ish OS.
Workaround exec issues on DOS-ish platforms

Apparently backick-based execution does not work with forward slashes.

Also adds a test for the "run" command on DOS-ish platforms, just
based on batch files (.bat) as I don't want to include .exe or .com
files.
Drop unneeded variable from t/win-functionality.t
Code-Deduplication: Add function dosish for the dos-ish test
RPP: Move variable initialisation behind the POD intro
RPP: Add POD section about file name constraints
Mention where the file name constraints are documented
Add new dos-ish test files to MANIFEST
Sort MANIFEST
Particularise build_requires to test_requires
Add a concat method

This is not a run-parts feature, but things like "cat `run-parts
somedir`" are used quite often and this method offers that.

This also adds the method to t/basic-functionality.t.

Needs File::Slurp. Added to requirements accordingly.
Rename internal function array_or_string to lines
concat+lines: Already let File::Slurp do the chomp
Simplify lines() to a one-line ?: instead of if/else
Move lines() to new Run::Parts::Common module

This adds a new test and run requirement on Exporter::Easy.