Support operators in Phabricator search

Summary:
Boolean search supports operators, such as phrase search.
It can be further improved by setting [[http://dev.mysql.com/doc/mysql/en/server-system-variables.html#sysvar_ft_boolean_syntax | ft_boolean_syntax]] to `' |-><()~*:""&^'` (note the leading space):
Default value uses no operator for "optional word" and `+` for "mandatory word".
This value uses no operator for "mandatory word" and `|` for "optional word".

Test Plan: Search for "Enter the name" (with quotes).

Reviewers: epriestley

Reviewed By: epriestley

CC: aran

Differential Revision: https://secure.phabricator.com/D2064

src/applications/search/engine/mysql/PhabricatorSearchEngineMySQL.php

@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -180,7 +180,7 @@ final class PhabricatorSearchEngineMySQL extends PhabricatorSearchEngine {
         "{$t_field} field ON field.phid = document.phid");
       $where[] = qsprintf(
         $conn_r,
-        'MATCH(corpus) AGAINST (%s)',
+        'MATCH(corpus) AGAINST (%s IN BOOLEAN MODE)',
         $q);
 
       // When searching for a string, promote user listings above other