semantic: string literal escape sequence handing

[bzz]

Discovered as part of the bblfsh/bblfshd#268 (comment)

This is an ☂️ issue for multiple driver failures \w invalid syntax.

E.g driver fails to parse e.g this file with

     check: key "value": invalid syntax

Normalization mapping for semantic mode needs to be updated.

• check: key "value": invalid syntax ("\0\0\0\0\0\0\0\0") Fix js-specific escape sequence handling #79
  double quoted literals need to have same js escape sequence handled as Handle quoting U+0000 properly #64
• check: key "value": invalid syntax ("\.\.")"
• ...

132 file examples could be obtained using

grep "language=javascript$" bblfshd.log | grep -oP "rpc error: code = \K(.*)" | grep "invalid syntax" | sort | less

[bzz]

PR description updated to become an ☂️ issue with multiple PRs fixing it.