Summary:
In MacOS, I got issue with `Footer`'s default constructor, which initialized the magic number with some random number instead of 0.
With investigation, I found we forgot to make the kInvalidTableMagicNumber to be static. As a result, kInvalidTableMagicNumber was assgined to `table_magic_number_` before it is initialized (which will be populated with random number).
Test Plan: passed current unit tests; also passed the unit tests for the incoming diff which used the default footer.
Reviewers: yhchiang
CC: leveldb
Differential Revision: https://reviews.facebook.net/D16077
aa734ce9ab