style: YYUSE is private, make it YY_USE

This macro is not exposed to users, make start it with 'YY_'.

* data/skeletons/bison.m4, data/skeletons/c.m4, data/skeletons/glr.c,
* data/skeletons/glr.cc, data/skeletons/glr2.cc, data/skeletons/lalr1.cc,
* src/parse-gram.c, tests/actions.at, tests/c++.at, tests/headers.at,
* tests/local.at (YYUSE): Rename as...
(YY_USE): this.

tests/actions.at

@@ -334,10 +334,10 @@ exp: { ]AT_CXX_IF([[std::cerr << @$ << '\n']],
 
 ]AT_YYLEX_PROTOTYPE[
 {]AT_PURE_IF([
-  YYUSE(lvalp);
-  YYUSE(llocp);], [AT_CXX_IF([
-  YYUSE(lvalp);
-  YYUSE(llocp);])])[
+  YY_USE (lvalp);
+  YY_USE (llocp);], [AT_CXX_IF([
+  YY_USE (lvalp);
+  YY_USE (llocp);])])[
   return 'x';
 }