Summary:
I want to be able to, e.g., DECLARE_string(statistics_string); in my application such that I can override the default value of statistics_string. For this to work, we need to remove the unnamed namespace containing all the flags, and make sure all variables/functions covered by that namespace are static.
Replaces #1828 due to internal tool issues.
Closes https://github.com/facebook/rocksdb/pull/1844
Differential Revision: D4515124
Pulled By: ajkr
fbshipit-source-id: 23b695e
d70ce7ee0b