Avoid creating intermediate strings in the PostScriptLexer
Merge pull request #5063 from Snuffleupagus/ps-parser-avoid-intermediate-string-creation

Avoid creating intermediate strings in the PostScriptLexer
Re-factor heuristics to recognize unknown glyphs for |toUnicode|
Adjust the heuristics to recognize more cases of unknown glyphs for |toUnicode| (issue 5070)