[DomCrawler] Fix relative path handling in links

Added relative path canonicalization according to RFC 3986, section 5.2.4
merged branch lazyhammer/crawler-relative-links-2.1 (PR #7244)

This PR was merged into the 2.1 branch.

Commits
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a4ec677 [DomCrawler] Fix relative path handling in links

Discussion
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[2.1][DomCrawler] Fix relative path handling in links

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7219
| License       | MIT
| Doc PR        | n/a

Added relative path canonicalization according to RFC 3986, section 5.2.4

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by vicb at 2013-03-02T14:48:46Z

@fabpot seems like 2.1 as a deps issue if you look at travis logs