Don't attempt hot backups on non-standard data types, that's an error now.
Add WT_PREFIX_MATCH_LEN, a version of WT_PREFIX_MATCH that doesn't go
past the specified length of the string.
Check we can't name checkpoints that include LSM tables.
Change the complex_populate fuction to optionally create LSM tables,
change the backup test to backup LSM trees.
Disallow hot backups in any tree that includes something other than a
"file" or "lsm" type or source entry.

LSM objects don't have "source=XXX" entries, so we can't use that to
figure out what files we need.  Rewrite the table-level backup to use
the table name in all cases, instead.  This isn't always going to work,
though, we could match non-unique table names, that is, "table_X" and
"table_XX" will both match a backup target of "table_X".