[HttpFoundation] fixed the creation of sub-requests under some circumstancies (closes #6923, closes #6936)

This fixes the creation of a sub-request when the master request Request URI
is determined with specific server information.
Add dot character `.` to legal mime subtype regular expression
merged branch romainneutron/file-binary-guesser (PR #7006)

This PR was merged into the 2.0 branch.

Commits
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a12744e Add dot character `.` to legal mime subtype regular expression

Discussion
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[HttpFoundation][2.0] Add dot character `.` to legal mime subtype regular expression

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

For example, the following mimetype (used for Microsoft powerpoints) is not recognized given the current regexp : `application/vnd.ms-powerpoint; charset=binary`