Enhance abseil-faster-strsplit-delimiter to handle other non-printable characters.
Currently it fails on cases like '\001'.
Note: Since StringLiteral::outputString dumps most nonprintable
characters in octal value, the exact string literal format isn't preserved,
e.g. "\x01" becomes '\001'.
Reviewed By: gribozavr
Subscribers: lebedev.ri, Eugene.Zelenko, cfe-commits
Differential Revision: https://reviews.llvm.org/D64151
Patch by Xiaoyi Zhang.