Changes

The Flow_sedlexing module is forked from the Sedlexing module, with the following changes:

• Removed encodings we don't need, e.g, Utf16, Latin1
• Removed bookkeeping fields which do not matter when everything is done in memory:
  • filename
  • finished
  • refilled (refill not needed either)
• Changed Uchar.t array to int array
• Added lexbuf_clone for internal usage
• Added
  • Utf8.lexeme_to_buffer
  • Utf8.lexeme_to_buffer2
• Rewrote utf8 encoding/decoding for performance