Predicate Escape::unescape

Reverse the escape operation on a string, using the escape map, and a custom escape character.

The escape character is also unescaped in the string when it is used to escape itself.

See the module documentation (Escape) for more details.

Note: adding pragma[inline_late] is very important for compilation speed. Otherwise, we hit pathological cases of possible binding sets after inlining every involved predicate, which must occur due to the bindingset. The performance effects of inline_late on callers has not yet been evaluated.