* configure.ac (GXX): Rename as...

* configure.ac (GXX): Rename as...
(CXX): this, to keep the original Autoconf semantics.
Require 2.57.
* data/lalr1.cc: Fix b4_copyright invocations.
If YYDEBUG is not defined, don't depend upon name_ being defined.
(location.hh): Include string and iostream.
(Position::filename): New member.
(Position::Position ()): New.
(operator<< (Position)): New.
(operator- (Position, int)): New.
(Location::first, Location::last): Rename as...
(Location::begin, Location::end): these, to mock the conventional
iterator names.
(operator<< (Location)): New.
* tests/atlocal.in (CXX): New.
* tests/testsuite.at (AT_COMPILE_CXX): New.
* tests/calc.at (_AT_DATA_CALC_Y): Adjust yyerror to report the
locations in a more synthetic way.
(AT_CHECK_PUSHDEFS): AT_YYERROR_SEES_LOC_IF is positive if
lalr1.cc is used.
Adjust the C locations to match those from Emacs: first column is
column 0.
Change all the expected results.
Conform to the GCS: simplify the locations when applicable.
(LOC, VAL, YYLLOC_FORMAL, YYLLOC_ARG, USE_YYLLOC, LEX_FORMALS)
(LEX_ARGS, USE_LEX_ARGS, LEX_PRE_FORMALS, LEX_PRE_ARGS): Replace
these CPP macros with the m4 macros new defined by...
(AT_CHECK_PUSHDEFS): this, i.e.:
(AT_LALR1_CC_IF, AT_PURE_LEX_IF, AT_LOC, AT_VAL, AT_LEX_FORMALS)
(AT_LEX_ARGS, AT_USE_LEX_ARGS, AT_LEX_PRE_FORMALSm AT_LEX_PRE_ARGS)
New macros.
(AT_CHECK_POPDEFS): Undefine them.
(AT_CHECK_CALC_LALR1_CC): New.
Use it for the first lalr1.cc test.