bug #11319 [HttpKernel] Ensure the storage exists before purging it in ProfilerTest
minor #11321 [HttpKernel] Ensure the storage exists before purging it in ProfilerTest (penyaskito)

This PR was merged into the 2.3 branch.

Discussion
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[HttpKernel] Ensure the storage exists before purging it in ProfilerTest

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11319
| License       | MIT
| Doc PR        | None

Commits
-------

eb63270 bug #11319 [HttpKernel] Ensure the storage exists before purging it in ProfilerTest
added XSD to PHPUnit configuration
minor #11329 add XSD to PHPUnit configuration (craue)

This PR was merged into the 2.3 branch.

Discussion
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add XSD to PHPUnit configuration

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | --
| License       | MIT
| Doc PR        | --

The syntax check functionality has been removed in PHPUnit 3.6 already. But there's no Composer constraint for PHPUnit, so you can never know which version will actually be used to run tests. Let me know what you think.

Commits
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84b5581 added XSD to PHPUnit configuration
removed defaults from PHPUnit configuration
updated CHANGELOG for 2.3.17
update CONTRIBUTORS for 2.3.17
updated VERSION for 2.3.17
bumped Symfony version to 2.3.18
minor #11344 remove defaults from PHPUnit configuration (craue)

This PR was merged into the 2.3 branch.

Discussion
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remove defaults from PHPUnit configuration

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | --
| License       | MIT
| Doc PR        | --

Follow-up to #11329.

Commits
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afc4930 removed defaults from PHPUnit configuration
[HttpFoundation] Remove content-related headers if content is empty
bug #11244 [HttpFoundation] Remove body-related headers when sending the response, if body is empty (SimonSimCity)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #11244).

Discussion
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[HttpFoundation] Remove body-related headers when sending the response, if body is empty

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

I've updated the implementation for informational and 204 or 304 responses. They will now, as they have no content, not return headers like `content-type` or `content-length`.

I'm unsure about `content-length` - we could also set it hardcoded to zero ... but I thought, that (because the specs say that it just can't have a response-body) the system should not return anything here.

Commits
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9dbe89d [HttpFoundation] Remove content-related headers if content is empty
fixed CS
[2.3][Form] Cleanup & fix phpdocs
[Upgrade] Fixed markdown syntax
minor #11359 [Upgrade] Fixed markdown syntax (lyrixx)

This PR was merged into the 2.3 branch.

Discussion
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[Upgrade] Fixed markdown syntax

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        |

Commits
-------

deb70c7 [Upgrade] Fixed markdown syntax
[HttpFoundation] Fix wrong assertion in Response test
minor #11358 [2.3][Form] Cleanup & fix phpdocs (stloyd)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Form] Cleanup & fix phpdocs

| Q             | A
| ------------- | ---
| Bug fix?      | kinda
| New feature?  | no
| BC breaks?    | no
| Tests pass?   | yes
| License       | MIT

This PR was done mostly cause of reports about invalid/not supported types/variables in phpstorm/scrutinizer-ci, and after I started fixing I noticed more problems in those phpdocs so I have cleanedup them a bit.

Commits
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a67bc76 [2.3][Form] Cleanup & fix phpdocs
fix issue #8171 on configuration tree for twig extension -- pairing up with @cordoval
added regression test