Fix E_STRICT warnings generated by static calls to non-static methods.

The PEAR::DB class implements several methods used in the static context without actually declaring them as static. This generates hundreds of calling non-static member from static context PHP warnings which in turn clog up the drupal_error_handler and watchdog systems. So make the methods static.

It is safe to do so because static methods can be called in a non-static context without warning or issue. Warnings are only generated when calling a non-static context from a static one.