[tmemfile] Disallow aggregate initialization for ExternalDataRange_t.
[tmemfile] Disallow aggregate initialization for ExternalDataRange_t.

This patch makes it more difficult for people to avoid the 'automatic' memory
ownership done by TMemFile. It forces people to explicitly construct the
data structure describing memory blob and makes it easier to grep for.

root-mirror/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,karies/root,olifre/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,karies/root,olifre/root,olifre/root,olifre/root,karies/root,karies/root,root-mirror/root,root-mirror/root,karies/root,karies/root