PUB-841: Add accessors and convenience functions.
PUB-841: Add tests for inflate_impl for all Chunks except C4FChunk, which isn't
ever created.
PUB-841: Add Chunk tests to JUnitRunnerDebug.
PUB-841: Fix chunks inflate_impl and NewChunk compression such that JUnit tests pass again.
PUB-841: Test NewChunk creation from sparse chunks in more depth.
PUB-841: More testing for C0L, C0D and CBS chunks.
PUB-841: Add tests that at() interface behaves the same as at0, at80, etc.
PUB-841:  Fix at() access of constant chunks or sparse NewChunk (swap the meaning of _len and _len2)

Before:
NewChunk._len: sparse length
NewChunk._len2: logical length

Now:
NewChunk._sparseLen: sparse length
NewChunk._len: logical length (same as all other Chunk._len)
PUB-841: Test NewChunk verbosely after inflation from all chunk types (where not already tested).
PUB-841: Fix NewChunk atd_impl (double), was falling back to at8_impl (long) even for negative exponent.  Would AIOOB.
Merge branch 'arno-chunks'
Merge branch 'master' of https://github.com/0xdata/h2o