[phobos] svn-->git migration

[Jason Evans]

I converted the druntime repository from svn to git a few days ago, and 
I'm doing the same for phobos and dmd today.  Please hold any pending 
changes you have until the conversion is complete, then commit your 
changes to the git repository.  See 
https://github.com/D-Programming-Language for more information about the 
git repositories.

For right now I'm focusing on getting the conversion done as quickly and 
smoothly as possible, but after it's done, I'll try to help people with 
general git configuration and work flow issues as necessary.

Thanks,
Jason