symm/: Allow block cipher and hash functions with strange names.

symm/: Allow block cipher and hash functions with strange names.

This is quite a performance, actually.

  * The `multigen' tool now has a modifier `:f' which makes a filename-
    safe version of a value.

  * The `multigen' input files and `Makefile.am' have been changed to
    use `:f' appropriately.

  * All of the `MUMBLE-def.h' header files have been changed to
    introduce a new macro `MUMBLE_DEFX' with two extra arguments: the
    thing's presentable name (for use in class structures), and a
    filename-safe version of it.  The old `MUMBLE_DEF' macro still
    exists for compatibility (has anyone else written a mode?).

  * Similar changes have been made to the testing machinery in `blkc.h'
    and `hash.h', but this still needs cleaning up somewhat.