Anubis / Anubis

Still to be done:
  - euclidian division for Nat.
  - interpretation of literal hexadecimal integers as Word64 and Word128.
  - 'tools/words.anubis' for extra operations.

corrected the problem of 'dot' followed by 'end of file'.

Functions modified accordingly.
Two new syscalls: sqlite3_errcode and sqlite3_errmsg.

it is enlarged (serialize.cpp: the macro 'check_serial'). Modified 'description.text'
accordingly.

Added some messages in sdbms.anubis and safe_save_retrieve.anubis (to be dropped later).