Use the C++ interface to snappy from C++

Including the C interface from C++ cause compilation on
some platforms since the C header use a trailing comma
in one of the enumerations, which is not allowed in C++

Change-Id: I97dd1184cb0afa0fd9b5df818f6966ac5eb113ce
Reviewed-on: http://review.couchbase.org/31580
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>