Statistic API change

FYI. I just changed how statistics are defined. This eliminates one static constructor for each statistic in the system, causing them to be statically initalized instead. To update any out of tree code, change this:

Statistic foo("blah", "desc");


#define DEBUG_TYPE "blah" // before any #includes
STATISTIC(foo, "desc");

Statistics are now implicitly declared static, so they can be moved out of anonymous namespaces and don't need explicit static qualifiers.

Lemme know if there are any questions. I will most likely be making similar changes for pass registration and command line options in the near future.