Print out a "waiting on stdin" message from 'arc call-conduit'

Summary: It looks like this command is just hanging if you skim the documentation and miss that you have to echo parameters into it. Print out a hint.

Test Plan: Ran `arc call-conduit` and got a hint.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9050
Fixed the error message when cppcheck isn't installed to not be completely wrong.

Summary: Arcanist is a dirty rotten liar.  I made it less of a dirty, rotten liar.

Test Plan: http://imgur.com/36qXcgI

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9081
Write waiting message to stderr, not stdout.
Rename test method.

Summary: Rename this test method for consistency with other linter test classes.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9095
Minor cleanup of linter testing code.

Summary:
Just some minor cleaning up, including:

- Removing old annotations for Diviner.
- Renaming some `lint-test` files so that the directory name bears a closer resemblance to that of the linter.
- Remove some useless `return` statements.

Test Plan: `arc unit`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9096
Read 'phabricator.uri' and 'default' out of more config sources

Summary: We have old/inconsistent code for reading these. Instead, read from sources in a modern way.

Test Plan:
  - Removed "default" and "phabricator.uri" from user/local/project config.
  - Set "default" in "/etc/arcconfig".
  - Ran `arc tasks` and got a "connect to Phabricator" message.

Reviewers: btrahan, davedash

Reviewed By: davedash

Subscribers: davedash, epriestley

Differential Revision: https://secure.phabricator.com/D9105
Support Checkstyle as an output format for lint results.

Summary: Fixes T4948. Add a lint renderer which supports outputting the lint results in the Checkstyle XML format.

Test Plan: Ran `arc lint --xml` and inspected the output.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4948

Differential Revision: https://secure.phabricator.com/D9083
Merge branch 'master' of github.com:facebook/arcanist