(input): Don't try to initialize yylloc here, do it in the
scanner.
* src/scan-gram.l (YY_USER_INIT): Initialize yylloc.
* src/gram.h (rule_t): Change line and action_line into location
and action_location, of location_t type.
Adjust all dependencies.
* src/location.h, src/location.c (empty_location): New.
* src/reader.h, src/reader.c (grammar_start_symbol_set)
(grammar_symbol_append, grammar_rule_begin, grammar_rule_end)
(grammar_current_rule_symbol_append)
(grammar_current_rule_action_append): Expect a location as argument.
* src/reader.c (grammar_midrule_action): Adjust to attach an
action's location as dummy symbol location.
* src/symtab.h, src/symtab.c (startsymbol_location): New.
* tests/regression.at (Web2c Report, Rule Line Numbers): Adjust
the line numbers.
