Code Review: StringGsubWithPattern

tfpt review “/shelveset:StringGsubWithPattern;REDMOND\dremy”
Comment :
Changes for string.gsub with pattern ruby specs to pass. The
following tests now pass:

String#gsub with pattern, replacement replaces & and \0 with the
complete match
String#gsub with pattern, replacement replaces ` with everything
before the current match
String#gsub with pattern, replacement replaces ’ with everything
after the current match
String#gsub with pattern, replacement replaces + with the last paren
that actually matched
String#gsub with pattern, replacement treats + as an empty string if
there was no captures
String#gsub with pattern, replacement maps \ in replacement to
String#gsub with pattern, replacement leaves \ at the end of
replacement untouched