License headers

[Olga Natkovich]

Hi,
 
In preparation for Pig release, I am checking the code to make sure that
all files have apache headers. I see a lot of newer files that don't.
 
Developers, please, make sure that all new files (both source and test)
include apache license header. You can copy one from an existing file.
Configuration and binary files don't require a header.
Committers, please, check the patches for license headers. (We should
automate this process similarly to hadoop.)
 
Thanks,
 
Olga