add old-soot escaping for LegacyJimplePrinter

[swissiety]

integrate legacy escapings from old soot into LegacyJimplePrinter

[cgobel]

In my case, exactly this leads to a problem when I try to read the produced jimple files with old soot in order to convert them back to Java or Android bytecode. I receive a ParserException which says it expects a quoted string for an identifier. It is quoted but old soot expects SINGLE quotes and sootup's JimplePrinter (even in legacy mode) uses DOUBLE quotes. But it seems to relate to methods that are named as keywords only (e.g. method names "of" or "from" from some Kotlin classes).