Get the PID properly on Android

- Related: #2109
Fix a bug where SpdyHeaderBlockZlibDecoder fails to decompress

- Forward-port 4c35b593c1ec811d1134cb0ef43db9329935e18e, originally written by @wgallagher
- Fixes #2077
Port the changes in SpdyHeaderBlockZlibEncoder to master & 4.0

Somehow it slipped away.
Port the changes in SpdyHeaderBlockRawDecoder to master & 4.0

Somehow it slipped away.
Fix a bug where DefaultChannelPipelineTest.testFireChannelRegistered() triggers channelRegistered() twice
Add missing validation which results in NPE later
Better exception message
Fix checkstyle
Use the source frame's allocator instead of the unpooled allocator
microbench: move from Caliper to JMH
Merge remote-tracking branch: upstream/master