Minor fix for Linux compilers

Adds a missing include for cstddef

Shared and weak pointer fixes

Fixes some races and reference counting issues in shared_ptr and weak_ptr

Fix NextSlot for out of message condition

This was broken by a recent change. Reverts the change. The subscriber needs to hold onto the last slot it saw so that NextSlot can refer to a valid slot. The slot can't be recycled.

Some bug fixes

Fixes problems with resizing.

A few bugs fixes and tidyups

Incorporates some changes from Mikael for MIRSA compliance and fixes a few bugs.

1.3.1: Fix dropped message detection

Fixes a small issue with dropped message detection (should only be reported when reading next, not newest messages).

Also, upgrades to latest coroutines and toobelt releases that fix bitset bugs.

Release 1.3.0

Fixes bug with creating unique files for shared memory files. On linux, creates a unique file in /dev/shm. On other systems, creates a file in /tmp.

On BSD systems it is not possible to check for uniqueness for shared memory files because they don't exist in the file system. This is the only way I can think of to do it, but will result in an accumulation of empty files in /tmp. Not a biggie, but I might need to tidy that up.

Release 1.2.9

Removes unnecessary memset from CCB allocation and fixes Ubuntu 18.04 build issue with common library.

Release 1.2.8

Uses new coroutine library that uses user contexts on linux and setjmp/longjmp on other OSes. Also minor tidyups.

Release 1.2.7

New version of cpp_toolbelt from Mikael.