diagnostics: %pure-parser is obsolete

Reported by Uxio Prego.
http://lists.gnu.org/archive/html/bug-bison/2018-12/msg00029.html

* src/scan-gram.l, src/parse-gram.y (PERCENT_PURE_PARSER)
(handle_pure_parser): New.
Issue a deprecation/update notice for %pure-parser.
* doc/bison.texi (Java Bison Interface): Don't mention %pure-parser.
* tests/actions.at, tests/input.at: Adjust.

tests/actions.at

@@ -1870,7 +1870,7 @@ AT_DATA_GRAMMAR([input.y],
 [[
 %define parse.error verbose
 %debug
-%pure-parser
+%define api.pure
 %code {
 # include <stdio.h>
 # include <stdlib.h>