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.

tests/input.at

@@ -2361,7 +2361,7 @@ m4_define([AT_CHECK_NAMESPACE_ERROR],
 [
 AT_DATA([[input.y]],
 [[%language "C++"
-%defines
+%header
 %define api.namespace {]$1[}
 %%
 start: %empty;
@@ -2908,6 +2908,7 @@ AT_DATA_GRAMMAR([[input.y]],
 %error-verbose
 %glr-parser
 %name-prefix "bar"
+%defines "header.h"
 %%
 exp : '0'
 ]])
@@ -2991,6 +2992,7 @@ AT_CHECK([sed -e '1,8d' input.y], [],
 %define api.pure
 %token-table
 %glr-parser
+%defines "header.h"
 %%
 exp : '0'
 ]])