[1.6.x] Fixed #21404 -- Added session.set_expiry() note to 1.6 release notes.

Thanks pwr for the suggestion.

Backport of ffdae5b66d from master
[1.6.x] Fixed #21240 -- Added 1.5 release note for OneToOneField/select_related change.

Thanks marcin at sokrates.pl.

Backport of ba63b9895b from master
[1.6.x] Fixed #20852 - Fixed incorrectly generated left quotes in docs.

Sphinx generates left single quotes for apostrophes after
code markup, when right single quotes are required. The
easiest way to fix this is just by inserting the unicode
character for a right single quote.

Instances of the problem were found by looking for
">&#8216;" in the generated HTML.

Backport of c33d1ca1d98003de29cdecb6080b52c5c52139bd from master.
[1.6.x] Added release note for TypedChoiceField coerce limitation

Thanks Elec for the report and Simon Charette for the review.
Refs #21397.
Backport of 4a00f132e0 from master.
[1.6.x] Added more internal links in the management command documentation.

Backport of bc0413cbc6fd472371e907f17303c5ddcc9b4642 from master.
[1.6.x] Added non-breaking spaces for humanize in Russian
[1.6.x] Fixed #21457 -- Allowed fixture file name to contain dots

Thanks Keryn Knight for the report.
Backport of 97ac22ebfc from master.
[1.6.x] Fixed typo in topics/http/sessions.txt.

Backport of 9348fc5628 from master