Bringing the test suite into line.

That's a couple hundred failures, mostly caused by my
messing up the way symbols are printed. More to come.

test/files/run/collection-conversions.scala reveals that
fallbackStringCanBuildFrom is adjudicating implicit conflicts
(e.g. between Seq and ParSeq on GenSeq) before they reach the
user. Nothing like a heaping spoonful of random unintended
behavior when it comes to software.