HEX-1832 Parse2 fix: handle empty files in multi file parse.
Added test case for multi file parse for parse 2 (we had test only for va parse). Added some empty files in the folder to make sure we handle that.
NewChunk compression fix: cancel sparse in compress if below required sparse ratio (instead of just going on with sparse representation).
Merge branch 'master' of github.com:0xdata/h2o