re2 build tuning

Shorten dfa_test, possible_match_test.

Split reasonably sized tests from huge tests
and run only the former by default.

Shared library hell.

GNU make variables.

Fixes issue 20.
Fixes issue 22.
Fixes issue 25.

R=r
CC=re2-dev
http://codereview.appspot.com/1853042
5 files changed