format-number of a value at or beyond 2^53 ran an unguarded
Double-to-Int conversion, a fatal trap reachable from user data; a
fraction picture beyond 15 places overflowed the scale conversion the
same way; and xsl:number value= beyond 2^53 trapped identically.
Digit extraction clamps fraction places to 15 (the 2^53 exactness
bound), pads back to the picture's minimum, renders out-of-range
integers through the exponent expander, and xsl:number falls back to
plain number rendering outside [1, 2^53). Sort-key rows always carry
one key per sort. Regression tests cover all three trap paths.
Mihaela Mihaljevic
b84fdd00ef