Unify Language/ examples output style

[Altai-man]

No more #->. No more #=>. No more # OUTPUT<<(all of these could be mixed even in a single file). Just our plain unified style described here: #776 (comment)
This is a final stage of formatting work, there will be (hopefully) no more such PRs.

[Altai-man]

The PR somewhat grew today, hence the explanation:

• New fixes for the examples.
• (important) The actual test of compiled examples was added.

This test:
1)Extracts examples from documentation;
2)Tries to compile it;
3)If the exitcode is 0, then it's okay, otherwise changes was bad.
We skip unsuitable or infinite examples by :skip-test directive. As for now, all documentation passes this test(with changes included in this PR).

Why do we need this? Okay, during my journey into the documentation, I've reviewed it entirely and found quite a lot of bugs, broken examples, mistakes in comments, etc. Documentation and code surely start to rot with time, but we can at least prevent this a little.

cast @AlexDaniel, @gfldex, @coke for reviewing, discussing, merging/rejecting.

[coke]

Looks good