doc: create a new Tuning LR section in the manual.

doc: create a new Tuning LR section in the manual.

And clean up all other documentation of the features described
there.
* NEWS (2.5): Tweak wording of lr.type and parse.lac entries a
bit, update the cross-references to the manual, and point out that
LAC has caveats.  Don't be so adamant that IELR+LAC=canonical LR.
That is, as the referenced section in the manual documents, LAC
does not fix infinite parsing loops on syntax errors.
* doc/bison.texinfo: Consistently drop the "(1)" suffix from LALR,
IELR, and LR in @cindex.
(%define Summary): Condense the entries for lr.default-reductions,
lr.keep-unreachable-states, lr.type, and parse.lac into brief
summaries, and cross-reference the appropriate subsections of
Tuning LR.  For parse.lac, mention that it's only implemented for
deterministic parsers in C.
(Error Reporting): When mentioning %error-verbose, mention LAC,
and add cross-reference to the LAC section.
(Tuning LR): New section with an extended version of the
documentation removed from %define Summary.  Change all
cross-references in the manual to point here instead of there.
(Calc++ Parser): When mentioning %error-verbose, mention LAC, and
add cross-reference to the LAC section.
(Table of Symbols): In %error-verbose and YYERROR_VERBOSE entries,
add cross-references to Error Reporting.
(Glossary): Capitalize entry titles consistently.  Add definitions
for "defaulted state" and "unreachable state".  Expand IELR
acronym in IELR's entry.