VOTable: Add a warning for integers that are out of range

As pointed out by Andy Ptak in the mailing list thread: "Problem reading VOTable produced by HLA", integers that are out-of-range can cause exceptions from Numpy on certain platforms.

To address this (i.e. not crash) as well as to make it more obvious that the VOTable file is malformed, this PR adds a new warning when an integer value is out of range for the size of the field, and also truncates the value to be within range.