lib/: implement warnings-by-default

[jkeenan]

In this ticket we will track our progress on implementing Objective 3, warnings-by-default, for tests in the lib/ directory in the core distribution. See that ticket for guidance on addressing warnings.

On Oct 11 I ran make test on the alpha-dev-03-warnings branch at commit 78482fc. I then chopped up the output into individual files, gzipped them, and placed them for your reference in this directory on my server.

By my count, the line count in the output file was 6659, which compares with a line count of 80 for the same group of files when I run make test on the alpha branch at commit c5c5fb4. So one, somewhat crude way of measuring our progress is how far we manage to reduce the line count in these test runs.

Acceptance Criteria: All tests for this subdirectory PASS; no tests emit warnings.

[jkeenan]

I've been poking away at this ticket in the jkeenan/gha-306-warnings-lib-20201025 branch. There are two files that, as expected, are generating an enormous number of warnings. I have created separate tickets for those two.

[jkeenan]

Pull request #348 should clear all but 2 test files underneath `lib'.

[jkeenan]

As of Jan 24 2021, the only unit tests not passing in the lib/ subdirectory in the alpha-dev-03-warnings branch are:

    ../lib/Tie/Array/std.t
    ../lib/warnings.t