[1.5.x] Fixed #17935 - Clarified intro of topics/files.txt.

Thanks guettli for the suggestion.

Backport of f7795e968d from master
[1.5.x] Fixed #20094 - Be more careful when checking for Iterator

Python 2.6 has some different behaviour when checking
isinstance(foo, collections.Iterator).
Backport of 829dc3c5 from master.
[1.5.x] Fixed #20108 -- Fixed filepath_to_uri decoding error

This was a regression due to unicode_literals usage. Thanks Ivan
Virabyan for the report and the initial patch.
Backport of 164528acc8 from master.
[1.5.x] Fixed docs template name typo

Backport of a907fa088e from master
[1.5.x] Added missing markup to docs.

Backport of 93cffc3b37 from master.
[1.5.x] Fixed #20048, #20060 -- Modified tests for contrib apps sensitive to custom User models.

Thanks to matiasb for the report of #20060 and the draft patch for #20048.

(cherry picked from commit 930af661abdb4eb7322f1ab06f21df9ed04af43d)
[1.5.x] Fixed #20119 -- Fixed typo in auth docs

Thanks vinyll for the report.
Backport of f670cce9f53 from master.
[1.5.X] Fixed signature of HttpResponse.set_signed_cookie in docs.

Backport of c5b2414a52 from master
[1.5.x] Fixed #20091 -- Oracle null promotion for empty strings

Backpatch of e17fa9e877e84e93b699c2bd13ea48dbbb86e451
Document password truncation with BCryptPasswordHasher
Merge pull request #961 from dstufft/document-bcrypt-truncation-1.5.x

Document password truncation with BCryptPasswordHasher
[1.5.x] Fixed #18985 -- ensure module level deprecations are displayed

Also don't compete with -W CLI option.

Thanks to Aymeric Augustin for the catch, and Claude Paroz for the patch.

Backport of e79b857a07905340556f781a7d63016236b21c61 from master.
[1.5.x] Fixed #20078: don't allow filtering on password in the user admin.

Backport of 9e462f810194800af30ea19a6fb8ac5697d839b4 from master.
[1.5.x] Fixed logging-related test failure introduced by e79b857.

Backport of 654d8e9.
[1.5.x] Correctly restore warning capture after logging tests.

This is a fix to the wrong behavior that 15c3906eeb introduced.

Backport of 4befef9 from trunk.
Updated translations from Transifex

Polish, Telugu, Georgian, Azerbaijani, Norwegian Bokmål, Basque,
Dutch, Thai, Spanish (Argentina), Afrikaans.
[1.5.x] Added 1.5.1 release notes.

Backport of ae5247cb from master.
Bump version numbers for 1.5.1.
Bumped version number post-release.
[1.5.x] Fixed #20146 -- Updated removed_tags example

Backport of e5d252f5b9 from master.