Use the last re2 tag before C++11 was introduced
Use the last re2 tag before C++11 was introduced

Recently (cd505f4597d) re2 was changed to use C++11 atomics, so before
we enable -std=c++11 in CFLAGS, prepare a release that explicitly checks
out the last tag (2016-02-01) before the change.

This is the commit which introduced C++11 atomics:
https://code.googlesource.com/re2/+/cd505f4597d4022902b25bd036de29478e22d481

tuncer/re2,tuncer/re2