Finer input type for yytranslate.

Finer input type for yytranslate.

This patch is debatable: the tradition expects yylex to return an int
which happens to correspond to token_number (which is an enum).  This
allows for instance to return characters (such as '*' etc.).  But this
goes against the stronger typing I am trying to have with the new
lex interface which return a symbol_type.  So in this case, feed
yytranslate_ with a token_type.

	* data/lalr1.cc (yytranslate_): When in %define lex-symbol,
	expect a token_type.