Plist inspection reported a serialized -0.0 real as the JSON number 0.
- The shared plist projection reports it as a typed real scalar whose value is the string -0, counted in a limitation for keyed archives and inspect_plist.
- The plutil JSON path applies the same value when it decodes -0.
- The XML decoder no longer returns -0 for a mixed-content integer.
Fixes#4834