Use PhutilQueryCompiler in Phabricator fulltext search

Summary:
Ref T11741. Fixes T10642. Parse and compile user queries with a consistent ruleset, then submit queries to the backend using whatever ruleset MySQL is configured with.

This means that `ft_boolean_syntax` no longer needs to be configured (we'll just do the right thing in all cases).

This should improve behavior with RDS immediately (T10642), and allow us to improve behavior with InnoDB in the future (T11741).

Test Plan:
  - Ran various queries in the UI, saw the expected results.
  - Ran bad queries, got useful errors.
  - Searched threads in Conpherence.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10642, T11741

Differential Revision: https://secure.phabricator.com/D16939

src/applications/search/controller/PhabricatorApplicationSearchController.php

@@ -317,6 +317,8 @@ final class PhabricatorApplicationSearchController
         $exec_errors[] = pht(
           'This query specifies an invalid parameter. Review the '.
           'query parameters and correct errors.');
+      } catch (PhutilSearchQueryCompilerSyntaxException $ex) {
+        $exec_errors[] = $ex->getMessage();
       }
 
       // The engine may have encountered additional errors during rendering;