改进where方法用法，支持更复杂的查询

Author: liu21st

ThinkPHP/Lib/Core/Db.class.php

@@ -423,6 +423,9 @@ protected function parseWhere($where) {
             }
             foreach ($where as $key=>$val){
                 $whereStr .= '( ';
+                if(is_numeric($key)){
+                    $key  = '_complex';
+                }                    
                 if(0===strpos($key,'_')) {
                     // 解析特殊条件表达式
                     $whereStr   .= $this->parseThinkWhere($key,$val);

ThinkPHP/Lib/Core/Model.class.php

@@ -554,7 +554,7 @@ protected function _parseOptions($options=array()) {
                     if(is_scalar($val)) {
                         $this->_parseType($options['where'],$key);
                     }
-                }elseif('_' != substr($key,0,1) && false === strpos($key,'.') && false === strpos($key,'(') && false === strpos($key,'|') && false === strpos($key,'&')){
+                }elseif(!is_numeric($key) && '_' != substr($key,0,1) && false === strpos($key,'.') && false === strpos($key,'(') && false === strpos($key,'|') && false === strpos($key,'&')){
                     unset($options['where'][$key]);
                 }
             }