add fast paths for W_IncrementalNewlineDecoder in W_TextIOWrapper._read_chunk

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branch : py3.7
2 jobs for branch/py3.7 in 7 minutes and 24 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #195245
check_rpython_annotations

00:07:24

passed #195246
hpy_tests

00:06:38