feature: 添加参数ignore_osc_alter_stmt可配置忽略osc的alter子句 (#258)

[hanchuanchuan]

添加参数ignore_osc_alter_stmt, 可配置强制忽略osc的Alter子句, 直接执行.

格式为drop index,add column等,配置要跳过的子句格式,多个时以逗号分隔

例 ignore_osc_alter_stmt = 'add index,drop index'

以下格式的语法已自动跳过osc:

ALTER TABLE tbl_name CHARACTER SET = charset_name;
ALTER TABLE tbl_name COLLATE = 'utf8_bin';
ALTER TABLE tbl_name COMMENT = '...';