Externs files now are dumped in an internal form rather than by

Externs files now are dumped in an internal form rather than by
converting them to SCode first.  This speeds up the process of
re-interning them.

Also, `sf' now maintains a database which allows the user to
programmatically specify syntax table and global declarations on a
per-filename basis.  This is used to eliminate `using-syntax' and
`integrate-external' occurrences in each file.