#16135: remove mentions of OS/2 from the documentation
merge 3.3
whatsnew: return types of re functions.
whatsnew: tarfile stat constants removal.
whatsnew: compression libraries support 'x' mode.
whatsnew: give Serhiy credit for audioop 24-bit sample support.
fix test on debug builds (closes #20731)
whatsnew: unittest discover works on namespace packages (#17457).

I also added the docs that never got committed, editing the patch provided by
Claudiu.

I collapsed the now three versionchanged directives for discovery into one.  I
tried several different styles for this.  The most obvious is a bulleted list,
but currently the only way I could find to produce that is to have *something*
appear on the versionchanged line after the colon, which combined with the
blank space before the bulleted list just looks wrong.  I also tried the
current single-line-three-sentences version with bullet characters before each
sentence, and I almost went with that as it made it clear that the three
sentences are independent.  But I decided to just go with the sentences for
simplicity reasons.
whatsnew: memoryview is Sequence and supports Reversed.
Issue #20465: Update OS X installer build to use SQLite 3.8.0.1.
Issue #20465: fix NEWS typo (it's 3.8.3.1)
fix test_posix.test_initgroups to work without supplemental groups (closes #20249)
merge 3.3 (#20249)
add Chris Angelico
merge 3.3