Fixes building under GCC 11

Include the most specific header documented by MSDN instead.

refactors GenerateOggSerial into a generic GenerateSerial
utility, under the util lib.

libFLAC may be encoded without Ogg support. If Ogg support is disabled,
libFLAC will still export Ogg-related methods (like setting a serial
number), and throw a runtime error when initializing an Ogg stream.

GenerateOggSerial does not depend on libogg. Refactoring it into
a generic GenerateSerial prevents having to add build-time checks
for libogg within the FLAC encoder plugin.

This is semi-standard and doesn't require the util/Compiler.h header.

This allows using it in constant expressions.

This makes it compatible with containers storing std::unique_ptr.

Replaces the static Duplicate() method.

To make things simpler, AllocatedString is now a non-template class.

By casting to SafeLinkIntrusiveListHook if appropriate, this fixes a
bug in the erase() method, where erase() calls
IntrusiveListHook::unlink() instead of
SafeLinkIntrusiveListHook::unlink().

The "std::nested_exception" catch block already covers this perfectly.

Similar to boost::intrusive::safe_link.