New command line program 'borotool'.
Added a test that crashes.
Allow NULLs in the v argument in boro_new().
Dump a slice of stdin after an importing error.
Revert "Dump a slice of stdin after an importing error."

This reverts commit 3f7ab3b9ae5b19089758110f89f12080ccdd9f21.
Fixed stupid bug in JSON blank parsing.
Removed begin and end when calling gc in borotool.
Ref then unref the root node in boro_end_rw() (to avoid crashing if it's the same).
Print some slice of stdin in JSON import error.
Added support for backslash-escaped chars in JSON string import.
Also allow signed numbers in JSON import.
New option 'tree' to borotool.
Some tweaks to CSV dump.
Avoid bus error in boro_mk_left() and boro_mk_right().
New option 'info' to borotool.
Minor output tweak to 'info'.
Reverse order in del_push().