Change the handling of the symbols in the skeletons.

Change the handling of the symbols in the skeletons.

Before we were using tables which lines were the symbols and which
columns were things like number, tag, type-name etc.  It is was
difficult to extend: each time a column was added, all the numbers had
to be updated (you asked for colon $2, not for "tag").  Also, it was
hard to filter these tables when only a subset of the symbols (say the
tokens, or the nterms, or the tokens that have and external number
*and* a type-name) was of interest.

Now instead of monolithic tables, we define one macro per cell.  For
instance "b4_symbol(0, tag)" is a macro name which contents is
self-decriptive.  The macro "b4_symbol" provides easier access to
these cells.

	* src/output.c (type_names_output): Remove.
	(symbol_numbers_output, symbol_definitions_output): New.
	(muscles_output): Call them.
	(prepare_symbols): Define b4_symbols_number.