Proton 0.7 tag and branch

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/0.7@1590055 13f79535-47bb-0310-9956-ffa450edef68
Reduced memory footprint of the TransportOutputAdaptor.

Before this change the TransportOutputAdaptor held a buffer of maxFrameSize
at all times. Because maxFrameSize can be quite large (1MB is quite normal)
this means it has a fairly high memory footprint considering that this
memory is hardly ever used, i.e. only when there is a frame to transfer and
in most cases the frame will not be maxFrameSize. Because the there is a
TransportOutputAdaptor for every connection the memory usage can become
quite high when dealing with many connections with large maxFrameSize (e.g.
1GB for only 1000 connections with a 1MB maxFrameSize).

This change is a classical tradeoff between memory usage and cpu cycles.
The memory usage has been reduced and the cpu usage increased. The buffer
is only allocated when it is needed and is released as soon as it holds no
more data. The code uses a small scratch buffer of 512 bytes to avoid
unnecessary allocations.
Removed unused member variable.
Reduced memory footprint of the FrameParser.

Before this change the FrameParser held a buffer of maxFrameSize at all
times. Because maxFrameSize can be quite large (1MB is quite normal) this
means it has a fairly high memory footprint considering that this memory
is hardly ever used, i.e. only when there is incoming data and in most
cases the frame will not be maxFrameSize.

This change is a classical tradeoff between memory usage and cpu cycles.
The memory usage has been reduced and the cpu usage increased. The buffer
is only allocated when it is needed and is released as soon as it holds no
more data.
Merge branch 'reduce_memory_consumption' into trunk