- error handler now looks for the @ operator that suppresses errors
- in php5 STRICT mode it throws a warning to pass an argument explicitely by reference. The refererence & is only necessary in the function definition
- added some help on how to install PDO on windows when PDO not enabled

git-svn-id: http://dev.piwik.org/svn/trunk@105 59fd770c-687e-43c8-a1e3-f5a4ff64c105