clang-format existing code in statsd.

Added .clang-format, because there isn't an official .clang-format file for Android framework code.

before we upload changes, do:

clang-format -style=file -i [file list]

to format the files that you touched.

Test: formatting only. NO code changes.
Change-Id: I90e87f1ee6618da8ea9bc2221c609c415a4046a8