[DBAL-1090] Changing string to fixed string is not recognized in PostgreSQL Platform

[SenseException]

The following change of an entity using PostgreSQL is not recognized by Doctrine DBAL:
from

    /**
     * @ORM\Column(type="string", name="name", length=2)
     */
    public $name;

to

    /**
     * @ORM\Column(type="string", name="name", length=2, options={"fixed"=true})
     */
    public $name;

A schema-update should change the column from character varying(2) to character(2) but instead acts like no changes were made on the column.

With this PR, I've extended the PostgreSqlPlatform to detect changes of the fixed option of a column.

[doctrinebot]

Hello,

thank you for creating this pull request. I have automatically opened an issue
on our Jira Bug Tracker for you. See the issue link:

http://www.doctrine-project.org/jira/browse/DBAL-1090

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included in.

[deeky666]

Why dloo1? Shouldn't it be name also?

[SenseException]

I must confess: I did evil copy paste. There's the reason why copy paste is an anti-pattern.

[deeky666]

@SenseException could you please make the new test case run on all platforms? You should put it into AbstractPlatformTestCase. This way we ensure, that this is working on all platforms. Thanks!

[SenseException]

@deeky666 I moved the test to AbstractPlatformTestCase and changed it into the style of the other test cases.

It looks like DrizzlePlatform has no tests at the moment. Is that correct?

[deeky666]

@SenseException looking good, merging. True, unfortunately we do not have a test class for the Drizzle platform yet :( So I'm fine with skipping it for the moment. Thanks!