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/synclines.at

@@ -452,9 +452,9 @@ m4_popdef([AT_TEST])
 m4_pushdef([AT_TEST],
 [AT_SETUP([%no-lines: $1])
 
-AT_BISON_OPTION_PUSHDEFS([%skeleton "$1" %defines])
+AT_BISON_OPTION_PUSHDEFS([%skeleton "$1" %header])
 AT_DATA_GRAMMAR([input.y],
-[[%skeleton "$1" %defines
+[[%skeleton "$1" %header
 %{
 ]AT_YYERROR_DECLARE_EXTERN[
 ]AT_YYLEX_DECLARE_EXTERN[