Exp: scalar encoding is incompatible with the parser rules

[andrus]

ExpScalar.toString doesn't follow the rules of the parser. It effectively calls value.toString(). The only special rule is that it encloses it in single quotes if it is a char sequence. We need the encoding to be complimentary to the literals grammar used by the parser:

Long l = 3147483647L; // encode as 3147483647L, not 314748364
BigDecimal d = new BigDecimal("2.1000001B"); // encode as 2.1000001B, not 2.1000001
// same for floats...

String s1 = "a'b"; // encode as "a'b", not 'a'b'
String s1 = "a\"'b"; // encode as 'a"\'b, not 'a"'b'