Reported by Heiko Becker <mail@heiko-becker.de> in
<https://lists.gnu.org/archive/html/bug-gperf/2025-04/msg00001.html>
and by Thomas Klausner <wiz@netbsd.org>.
* src/output.cc (Output::output_hash_function): Emit a
'defined __STDC_VERSION__' before the test of __STDC_VERSION__.
* tests/c-parse.exp, tests/charsets.exp, tests/chill.exp,
tests/cplusplus.exp, tests/java.exp, tests/languages.exp,
tests/modula2.exp, tests/objc.exp: Update.