Changes:

   * Specify #:scope when registering, not when creating filters

   * s/add-frame-filter!/register-frame-filter!/

   * s/remove-frame-filter!/unregister-frame-filter!/

   * Add s/set-frame-filter-enabled!/

   * Adapt for new TRY/CATCH/END_CATCH

   * Build with -Wunbound-toplevel, except for gdb.scm

Cheers,

Andy