CRM_Core_Error checks incorrect mysql_error

When a SQL error arises, CRM_Core_Error::handle() attempts to look up details using a low-level MySQL API. The code tries to detect "mysql" or "mysqli", but the check is wrong, which should produce two different errors:

• In PHP 7.x sites, it should crash due to the unrecognized function.
• In PHP 5.x sites, it should fail to report the actual error message (because it may check the wrong function).