Correct Profile class usage example. Addresses issue #18033.
Patch contributed by Olivier Hervieu and Dmi Baranov.
Close #18952: correctly download test support data

When test.support was converted to a package, it started silently
skipping the tests which needed to download support data to run.

This change refactors the affected code, and also tidies up
test.support.findfile to remove the unused *here* parameter, document
the *subdir* parameter and rename the *filename* parameter to avoid
shadowing the file builtin and be consistent with the documentation.

The unexpected skips were noticed and reported by Zachary Ware
Fix the dead link of IEEE_854-1987 standard with the Wikipedia entry.
Addresses issue #18438
Fixed tests with Tcl/Tk <8.5 (closes #18964).
Fix a typo. (closes #18953)