cpp/io/basic syncbuf/basic syncbuf

@1@ Default constructor: creates an instance of with emit-on-sync policy set to, wrapped streambuffer set to , and using default-constructed  as the allocator for temporary storage. @2,3@ Creates an instance of with emit-on-sync policy set to, wrapped streambuffer set to , and using  as the allocator for temporary storage. @4@ Move constructor: move-constructs a object by moving all contents from another  object, including the temporary storage, the wrapped stream pointer, policy, and all other state (such as the mutex pointer). After move, is not associated with a stream, and. The put area member pointers of the base class std of are guaranteed to be null. Destroying a moved-from will not produce any output.

Exceptions
@2,3@ May throw std from the constructor of the internal temporary storage or std from the mutex construction.