* data/glr.c (b4_shared_declarations): Put start-header first,

* data/glr.c (b4_shared_declarations): Put start-header first,
before any #includes that we generate, so that feature-test
macros work.  Problem reported by Michael Deutschmann in
<http://lists.gnu.org/archive/html/bug-bison/2006-09/msg00004.html>.
* data/lalr1.cc: Likewise.
* doc/bison.texinfo (Prologue): Document that feature-test macros
should be defined before any Bison declarations.
* tests/actions.at (_AT_CHECK_PRINTER_AND_DESTRUCTOR): Put defns
that depend on location.hh after, not before, Bison decls, since
we now include location.hh after the first user prologue.