Attaching lineno to buckets is stupid, since only one copy of each

Attaching lineno to buckets is stupid, since only one copy of each
symbol is kept, only the line of the first occurrence is kept too.
* src/symtab.h, src/symtab.c (bucket): Remove the line member.
* src/reader.c (rline_allocated): Remove, unused.
(symbol_list): Have a `line' member.
(symbol_list_new): New.
(readgram): Use it.
* src/print.c (print_grammar): Output the rule line numbers.
* tests/regression.at (Solved SR Conflicts)
(Unresolved SR Conflicts): Adjust.
Reported by Hans Aberg.