Refactor to reduce memory consumption

Hi,

I'm using libPhoneNumber quite extensively in a new project. After analyzing my app's resource consumption it occurred to me that libPhoneNumber is quite memory-intensive. I did some basic refactoring to on the static variables and especially on the way the regular expressions are initialized. As a result the memory consumption of libPhoneNumber in my app was reduced by ~40%. This was just a first shot and I think more work can be done here in the future, but it's sufficient for me for now.

You might want to take at the changes I made and merge them into the project.

Regards,
Frane