liburing: add extern "C" to liburing.h
liburing: add extern "C" to liburing.h

Make header includable from C++ projects.

Signed-off-by: Kevin Vigor <b1735822873657b2ba4cb3edb637a88fa594bbd8@gmail.com>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing