NITF DESDATA segments can be really large for LiDAR files

[hobu]

The DESDATA are currently being escaped, and for large LiDAR files, this causes the allocation of the escaped string to overflow. Instead of returning NITF_DESDATA for cases where the DESDATA is > 10mb, we should instead return the offset and byte length of the DESDATA for the user to go fetch themselves.

[hobu]

We will instead add NITF_DESDATA_OFFSET and NITF_DESDATA_LENGTH metadata entries in the case where the DESDATA is > 10mb.

[hobu]

Fixed in r24911 and backported in r24912.

[hobu]

Tweaked in r24913 and r24914.

[hobu]

const warning killed in r24915 and r24916