Allow MSVC users to build a DLL automagically.
Allow MSVC users to build a DLL automagically.

Many thanks to Richard Thiebaud for investigating this solution
as well as various other possibilities along the way.

Fixes #66.

Change-Id: I07d9a9eb675165d13c76b41372378f05fdb8f604
Reviewed-on: https://code-review.googlesource.com/7399
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2