tests: dispatch per lang on AT_DATA_GRAMMAR

* tests/java.at: Do that.
* tests/conflicts.at: Simplify.

* tests/actions.at, tests/c++.at, tests/input.at, tests/local.at,
* tests/named-refs.at:
Use AT_BISON_OPTION_PUSHDEFS/AT_BISON_OPTION_POPDEFS.

tests/c++.at

@@ -1347,6 +1347,7 @@ m4_popdef([AT_TEST])
 
 AT_SETUP([[C++ GLR parser identifier shadowing]])
 
+AT_BISON_OPTION_PUSHDEFS
 AT_DATA_GRAMMAR([input.yy], [
 %skeleton "glr.cc"
 
@@ -1386,6 +1387,7 @@ int main ()
 AT_BISON_CHECK([[-o input.cc input.yy]])
 AT_FOR_EACH_CXX([AT_COMPILE_CXX([[input]])])
 
+AT_BISON_OPTION_POPDEFS
 AT_CLEANUP