[1.5.x] Fixed #18949 -- Fix broken test interactions in ModelForms tests

A test in Model Forms test was specifically referring to a fixed
primary key, which was now being used up in a newly committed.
This has been worked around by specifying a higher primary
key.
[1.5.x] Fixed py3 compatibility for 5a00a57aa591c766f5ee1d8c59b64618d74fe191
[1.5.x] Fixed #8627 -- Prevented textareas to swallow first newline content

Browsers consider the first newline in textareas as some display
artifact, not real content. Hence they are not sending it back to
the server. If we want to keep initial newlines, we have to add one
when we render the textarea.
Thanks bastih for the report and initial patch.

Backport of 78f66691ee from master.
[1.5.X] Fixed #15591 - Clarified interaction between ModelForm and model validation.

Backport of d3fd8a1512 from master
[1.5.x] Fixed #19254 -- Bug in SESSION_FILE_PATH handling.

Thanks simonb for the report.

Refs #18194.

Backport of 11fd00c from master.
[1.5.X] Fixed #19246 - Updated SECURE_PROXY_SSL_HEADER example to use 'X-Forwarded-Proto'

Thanks Fred Palmer for the report.

Backport of 2cc1884383 from master
[1.5.x] Fixed #14315 -- Made memcached backend handle negative incr/decr values

Thanks Michael Manfre for the report and initial patch and
Tobias McNulty for the review.

Backport of 79dd751b0b from master.
[1.5.X] Fixed #19154 - Noted commit_manually requires commit/rollback for reads

Thanks als for the report.

Backport of 620e0bba49 from master
[1.5.X] Fixed #15968 - Noted that readonly_fields are excluded from the ModelForm

Backport of a386675a6a from master
[1.5.X] Fixed #19161 - Added missing clean_password method in custom user docs

Thanks DavidW for the report.

Backport of e8f696097b from master
[1.5.x] Fixed #19257 -- Don't swallow command's KeyError in call_command

Thanks Giovanni Bajo for the report.
Backport of 9a09558e9f from master.
[1.5.x] Fixed #19115 -- Documented stdout/stderr options for call_command

Thanks d1ffuz0r for helping with the patch.
Backport of b1ac329ba from master.
[1.5.x] Fixed #17144 -- MySQL again groups by PK only

Thanks to Christian Oudard for the report and tests.

Backpatch of [cafb266954e21dd55ddfa90597bcf02c022bcb7d]

Conflicts:

	django/db/models/sql/compiler.py
[1.5.x] Fixed #19266 -- Added Texinfo documentation target

Thanks orontee for the report and initial patch.
Backport of a79d920a56 from master.
[1.5.x] Merge pull request #506 from gwrtheyrn/ipv6_doc_fix

Fixed invalid ipv4 mapped ipv6 addresses in docs

Backport of 19eb56a277291de8c25a0edcc7af111dac7518af from master
[1.5.X] Added missing encoding preamble to gis tests.

'coverage html' did fail without it.

Thanks to Claude Paroz for figuring it out.

Backport of aea8bf06620c931f7b1e7d991497d593b91f71c9 from master.
[1.5.x] Merged pagination tests

It is simpler/cleaner to have all pagination tests in a single file.
Refs #16122.
Backport of 45802e12481 from master.
[1.5.x] Fixed #19261 -- Delayed Queryset evaluation in paginators

Thanks trbs for the report and the patch.
Backport of 1b307d6c8f from master.
[1.5.x] Fixed #19262 -- Support cookie pickling in SimpleTemplateResponse

Refs #15863.
Backport of 4d817b3887 from master.
[1.5.x] Fixed #14264 -- Ensured settings.configure configures logging

Thanks Matt McDonald for the patch.
Backport of 34162698c from master.