Minor linter fix

Summary: Self-explanatory

Test Plan: `arc lint`

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10942
Support an explicit connection timeout parameter for database connections

Summary:
Ref T6238. On the instance management interface, I want to check if an instance's database is reachable by connecting to it.

If it isn't, we hang for 30-60 seconds (default connection timeout). Allow explicit specification of a timeout when establishing a connection instead.

This only does MySQLi, not MySQL. We don't need MySQL for now, although it would be nice to support it eventually (Ref T6710).

Test Plan:
  - Browsed around.
  - Used short timeouts to get instance database status in instance management.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6238, T6710

Differential Revision: https://secure.phabricator.com/D10944
Allow ConduitClient to specify an explicit Host

Summary:
Ref T2783. To query a repository, we want to connect to a node which hosts it, but also connect using the correct instance hostname.

Allow `ConduitClient` to specify an explicit hostname.

Test Plan:
Used a script like this to verify that `setHost()` is impactful:

```
<?php

require_once 'scripts/__init_script__.php';

$response = id(new ConduitClient('http://127.0.0.1/'))
  ->setHost('local.phacility.com')
  ->callMethodSynchronous('conduit.ping', array());

var_dump($response);
```

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2783

Differential Revision: https://secure.phabricator.com/D10960
Use more liberal whitespae detection for `%%%` and `---` remarkup rules

Summary: This relaxes detection of whitespace for literal blocks and horizontal lines. In particular, when these rules are quoted, they appear as, e.g., `> ---`, which currently does not show a quoted horizontal line.

Test Plan: Added and ran unit tests. Quoted literal and HR rules.

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10972