doc/pipelining.dox: Fix reference to old API
ut-pipelining: Use an enum as a tag instead of a struct

Passing a null reference is undefined behavior.
compressor_request: Ensure requests are size_t-aligned
Initialize bool members in uncompressed_stream

uncompressed_stream::swap would read and write illegal bool values
(that are not 0 or 1) otherwise.
parallel_sort::sortWork: Handle n=0 case

log(0) returns -nan which cannot be converted into an int.
pipeline::fetch: Do not pass a temporary to boost::any_cast

boost::any_cast<T>(const any<T> &) coerces the payload to be const,
which is invalid if the wrapped object was not originally const.

This happens e.g. when boost::any contains an int which is wrapped in a
boost::any::holder<int>;
boost::any_cast<int>(const any<int> &) will try to coerce this into a
boost::any::holder<const int>
which results in undefined behavior.
Do not access a static member through a null pointer

This is probably always safe in practice, but the standard does not
specify anything for this corner case.
serialization: Do not dereference iterators pointing to null