Added an option to configure error types for registerShutdownFunction

The default error list includes E_STRICT, which is not something that everyone will need to use.

There's also an issue opened for it (see #168), so basically I've kept the current list as default and added an extra parameter on registerShutdownFunction to overwrite it.
Merge pull request #1 from pauloschilling/patch-1

Added an option to configure error types for registerShutdownFunction