Fix typo when closing config_parser handle, complain if the
config_parser.close method errors.
Allow overlapping strings when setting a buffer's contents, it's not
insane __wt_buf_set might be used to shuffle strings in an existing
WT_ITEM buffer.  Reference #881, but this doesn't close it, we still
want to understand why it can happen.
Merge branch 'develop' into new-split