* channel close race and deadlock fixes
* remove send lock, write chunks in one go
* push some of half-closed implementation to BufferStream
* fix some hangs where LPChannel readers and writers would not always
wake up
* simplify lazy channels
* fix close happening more than once in some orderings
* reenable connection tracking tests
* close channels first on mplex close such that consumers can read bytes
A notable difference is that BufferedStream is no longer considered EOF
until someone has actually read the EOF marker.
* docs, simplification
Dmitriy Ryajov
Jacek Sieka