[HttpFoundation] fixed the creation of sub-requests under some circumstances for IIS
merged branch bendavies/iis-rewrite-subrequests (PR #7606)

This PR was merged into the 2.1 branch.

Discussion
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[HttpFoundation] fixes creation of sub requests under IIS & Rewite Module

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6936, #6923
| License       | MIT
| Doc PR        | N/A

There are a few bugs to address.

1. `HTTP_X_ORIGINAL_URL` wasn't removed from the server parameters, so is picked back up [here](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/HttpFoundation/ServerBag.php#L33) upon recreation of a sub request.
2. When `X_ORIGINAL_URL` is passed in the headers by IIS, `IIS_WasUrlRewritten` and `UNENCODED_URL` can also be passed as server vars, so they must also be removed for sub request URI's to be resolved correctly.

Additionally, I have removed the OS check for windows, because it was only done for 2 out of 4 of the IIS specific checks, and it made the code untestable.

Also added tests for all scenarios as there were none.

Commits
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9fcd2f6 [HttpFoundation] fixed the creation of sub-requests under some circumstances for IIS
[HttpFoundation] fixed empty domain= in Cookie::__toString()
[HttpFoundation][BrowserKit] fixed path when converting a cookie to a string

An empty path has a different meaning than a /; it means that the path
is the one from the current URI.
Merge branch '2.1' into 2.2

* 2.1:
  [HttpFoundation][BrowserKit] fixed path when converting a cookie to a string
  [BrowserKit] removed dead code
  [HttpFoundation] fixed empty domain= in Cookie::__toString()
  fixed detection of secure cookies received over https
  [Translation] removed an uneeded class property
  [Translation] removed unneeded getter/setter
  [Translator] added additional conversion for encodings other than utf-8
  fix a DI circular reference recognition bug
  [HttpFoundation] fixed the creation of sub-requests under some circumstances for IIS
Merge branch '2.2'

* 2.2:
  [Config] #7644 add tests for passing number looking attributes as strings
  [HttpFoundation][BrowserKit] fixed path when converting a cookie to a string
  [BrowserKit] removed dead code
  [HttpFoundation] fixed empty domain= in Cookie::__toString()
  fixed detection of secure cookies received over https
  [2.2] Pass ESI header to subrequests
  [Translation] removed an uneeded class property
  [Translation] removed unneeded getter/setter
  [Translator] added additional conversion for encodings other than utf-8
  fixed source messages to accept pluralized messages [Validator][translation][japanese] add messages for new validator
  fix a DI circular reference recognition bug
  [HttpFoundation] fixed the creation of sub-requests under some circumstances for IIS

Conflicts:
	src/Symfony/Component/HttpFoundation/Tests/CookieTest.php
[2.3][HttpFoundation] PDO Session handling enhancements
merged branch MidnightLightning/master (PR #7634)

This PR was squashed before being merged into the master branch (closes #7634).

Discussion
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[2.3][HttpFoundation] PDO Session handling enhancements

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

`PdoSessionHandler` class assumes that the PDO object is set to throw exceptions, not errors. I added a line in the constructor to set that attribute, so configuration/query errors are able to be seen and caught a lot easier.

Commits
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ce8a441 [2.3][HttpFoundation] PDO Session handling enhancements