fail if int overflow in _longNameOffset

[pjfanning]

• relates to NegativeArraySizeException and ArrayIndexOutOfBoundsException in ByteQuadsCanonicalizer #1289
• the class relies on an array so can't handle the case where _longNameOffset ends up greater than Integer.MAX_VALUE
• I think it is helpful to fail with a readable exception - instead of array size exceptions
• It may or may not be useful to include details about how to disable canonicalisation

Only people who are seriously abusing JSON and creating names in their JSON that exceed 2 billion chars will hit this.

[cowtowncoder]

Looks good -- I'll modify message slightly but logic is solid!

[cowtowncoder]

Good idea: will merge.