Normalize SSE support detection
authorOrvid King <blah38621@gmail.com>
Tue, 28 Jul 2015 21:23:14 +0000 (14:23 -0700)
committerfacebook-github-bot-1 <folly-bot@fb.com>
Tue, 28 Jul 2015 22:22:19 +0000 (15:22 -0700)
commitf9651857d7a364e91ca74d07ad77765caf5fb161
treebf17073fe4347e42c75386de18554073ed573ba2
parent0c1113b9d64f7c805f1030f28329198fa2dd926d
Normalize SSE support detection

Summary: This unifies ways of detecting SSE support into the FOLLY_SSE define which is a numeric value from 0 to 4.2 depending on detected level.
This also adds a `#define` for `__extension__` which is used in folly, but is GCC specific.
Closes #259

Reviewed By: @yfeldblum

Differential Revision: D2283522

Pulled By: @sgolemon
folly/GroupVarint.h
folly/Portability.h
folly/RWSpinLock.h