* contrib/hbbtree/hb_btree.c
* read-only flag is not hidden when a file is opened
* allow skip size to be optional
* raise error when inserting or deleting into a read-only file
! this does not apply to a created read-only file
* improved argument checks
* fixed TOFIX regarding portable binary format reading/writing
* fixed TOFIX regarding a suspicious sizeof of a constant
! TOFIX: in-memory btree's cause a fatal error; this is a work in progress
20df4144ca