deprecate %defines in favor of %header

This is consistent with --defines being deprecated in favor of
--header.  The directive %defines is also too similar to %define.
And %header matches nicely with api.header.name.

* src/scan-gram.l (%defines): Deprecate to %header.
(%header): Scan it.
* src/parse-gram.y (PERCENT_DEFINES): Replace with...
(PERCENT_HEADER): this.
* data/skeletons/lalr1.java
* doc/bison.texi
* tests/actions.at, tests/c++.at, tests/calc.at, tests/conflicts.at,
* tests/input.at, tests/java.at, tests/local.at, tests/output.at,
* tests/synclines.at, tests/types.at:
Convert most tests to check %header instead of %defines.

etc/bench.pl.in

@@ -581,7 +581,7 @@ sub generate_grammar_list ($$@)
     or die;
   print $out <<EOF;
 %language "C++"
-%defines
+%header
 %locations
 $directives