* src/gram.c: Remove comments that duplicate comments in gram.h.

* src/gram.c: Remove comments that duplicate comments in gram.h.

When reporting useless rules and nonterminals, say "useless in grammar"
instead of "useless", and say "useless in parser" instead of "never
reduced".  Discussed starting at
<http://lists.gnu.org/archive/html/bison-patches/2007-10/msg00033.html>.
* NEWS (2.3a+): Mention this change.
* data/xslt/xml2text.xsl: Update output text and expected input XML
element names to match changes below.
* data/xslt/xml2xhtml.xsl: Likewise.
(xsl:template match="bison-xml-report"): Add missing entry in Table of
Contents: "Rules useless in parser due to conflicts".
* doc/bison.texinfo (Decl Summary): Reword a little.
(Understanding): Update example output for changes below.
* src/gram.c: (rule_useful_p): Rename to...
(rule_useful_in_grammar_p): ... this.
(rule_useless_p): Rename to...
(rule_useless_in_grammar_p): ... this.
(rule_never_reduced_p): Rename to...
(rule_useless_in_parser_p): ... this.
(grammar_rules_print): Update for renames.
(grammar_rules_print_xml): Update for renames.
(grammar_rules_never_reduced_report): Rename to...
(grammar_rules_useless_report): ... this since it is used for either
kind of useless rule.
* src/gram.h: Reword comments and update function names in prototypes.
* src/main.c (main): Say "rule useless in parser due to conflicts".
* src/print-xml.c (print_rules_never_reduced): Rename to...
(print_rules_useless_in_parser): ... this, and rename output XML
element "rules-never-reduced" to "rules-useless-in-parser".
(print_xml): Update for rename.
* src/print.c (print_results): Say "Rules useless in parser due to
conflicts".
* src/reduce.c (reduce_grammar_tables): Say "rule useless in grammar".
(nonterminals_reduce): Say "nonterminal useless in grammar".
(reduce_output): Say "Nonterminals useless in grammar".
Say "Rules useless in grammar".
(reduce_xml): Rename output XML element "useless" to
"useless-in-grammar".
(reduce_print): Don't report the count of grammatically useless rules
as "rules never reduced" just because %yacc is specified.
In the correct report of this count, say nonterminal(s) and rule(s)
"useless in grammar".
* tests/conflicts.at (S/R in initial): Update expected output.
(Defaulted Conflicted Reduction): Likewise.
(Unreachable States After Conflict Resolution): Likewise.
* tests/existing.at (GNU pic Grammar): Likewise.
* tests/reduce.at (Useless Nonterminals): Likewise.
(Useless Rules): Likewise.
(Reduced Automaton): Likewise.
(Underivable Rules): Likewise.
(Empty Language): Likewise.