Assert: fixed exception() return

33 threads as default

A method-level data provider returning an empty array or an empty
Traversable made runTest() return without calling the test method, and
run() printed a passing mark. It now throws TestCaseException, the same
way as an empty file-level data provider fails the test.

Typo in word "handler"

It now allows SVG, MathML and Custom Elements.

Fixup for 9d21094c99143616bec343baedeffaa9c70e3080

Runner shows 'No tests found' although pre-failed exists.

With follow: true, curl returns header blocks of all responses in the
redirect chain (and interim responses like 100 Continue), and they were
merged into one array, so e.g. Location of the 302 response was visible
after following it. Now each status line resets the parsed headers.

A header sent multiple times (e.g. Set-Cookie) is combined into one
comma-separated value instead of keeping only the last one.