XPath 1.0 4.2: an integer-valued number converts to a string with no decimal
point. The formatter only took the integer branch for a magnitude below 1e15,
so a value like 1234567890123456 (exact in a double, which holds integers
exactly to 2^53) printed as 1234567890123456.0. Raise the bound to 2^63, the
range where the Int64 conversion is safe; larger magnitudes still expand
through the exponent path.
Closes Apache Xalan conformance case string132.
Mihaela Mihaljevic
95fde5b177