… are set (weaverryan)

This PR was merged into the 2.8 branch.

Discussion
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[DependencyInjection] Fixing autowiring bug when some args are set

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #17724, #17878
| License       | MIT
| Doc PR        | todo

This fixes #17724 & #17878.

**#17724**

I've set this against the 2.8 branch because imo it's a bug fix. The [test](https://github.com/symfony/symfony/compare/2.8...weaverryan:auto-wiring-individuals?expand=1#diff-d124c3d39cd5f7c732fb3d3be7a8cb42R298) illustrates the bug - having *some* arguments set beforehand caused auto-wired arguments to be set on the wrong index.

**#17878**

I've also included this fix just to get all the weird ordering problems taken care of at once. I don't think this is a behavior change - autowiring with scalars only worked previously if the argument was optional (still works now) or if you specified that argument explicitly (still works). Otherwise, your argument ordering would have gotten messed up.

Commits
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260731b minor changes
865f202 [#17878] Fixing a bug where scalar values caused invalid ordering
cf692a6 [#17724] Fixing autowiring bug where if some args are set, new ones are put in the wrong spot

* 2.8:
  fixed issue with PHP 5.3
  The WebProcessor now forwards the client IP
  minor changes
  [#17878] Fixing a bug where scalar values caused invalid ordering
  [#17724] Fixing autowiring bug where if some args are set, new ones are put in the wrong spot
  bumped Symfony version to 2.3.39
  updated VERSION for 2.3.38
  update CONTRIBUTORS for 2.3.38
  updated CHANGELOG for 2.3.38

* 3.0:
  fixed issue with PHP 5.3
  The WebProcessor now forwards the client IP
  minor changes
  [#17878] Fixing a bug where scalar values caused invalid ordering
  [#17724] Fixing autowiring bug where if some args are set, new ones are put in the wrong spot
  bumped Symfony version to 2.3.39
  updated VERSION for 2.3.38
  update CONTRIBUTORS for 2.3.38
  updated CHANGELOG for 2.3.38