StreamingZipInflater: fix mmap'd end of read

When reaching the end of a mmap'd segment, it was erroneously trying to
read more data. This is because we were reading data one character at a
time, so we never reached the Z_STREAM_END result without going through
the loop once more.

Bug: https://code.google.com/p/android/issues/detail?id=39041
Change-Id: I6c53b8187384a42217c32112d6a0c2857f471109