Minor updates

A few portability updates and fix for small block header decoding for vector capacity.

Bitmap allocator in PayloadBuffer

This adds an optional bitmap allocator to the PayloadBuffer class. A bitmap allocator uses a set of fixed size blocks to hold allocations that are less than or equal to the configured size. It has a bitmask specifying which blocks are allocated. It's about twice the speed of a simple free-list allocator but at the expense of using more memory in the buffer. That's fine if you are creating messages in shared memory where the message size isn't important, but could be a hinderance if you want smaller messages that go over a network.

Variable sized socket buffers and experimental bitmap allocator

This adds a variable sized socket receive function that allocates a vector of char to receive a message.

Also adds an experimental bitmap allocator to the payload buffer, but this is switched off for now until it works fully. Should speed
up allocations of small blocks by a factor of 2 but at the expense of bigger messages.

Payloadbuffer resize fix

Fixes an issue with resizing a payload buffer.

PayloadBuffer class

This adds a PayloadBuffer class for use with zero-copy messaging protocols.

PayloadBuffer on Linux

1.1.9

Add missing includes

PayloadBuffer class

1.1.8

Add PayloadBuffer class

FileDescriptors and coroutines

Incorporates some fixes for FileDescriptors and uses new coroutines library.

Also adds some fixes from Mikael.

Minor bug fixes

Fixes a few minor bugs with invalid address detection in sockets.

SharedPtrPipe class

This adds a SharedPtrPipe class which allows std::shared_ptr object to be carried by a pipe. It is useful for communicating between coroutines.