also support $<foo>$ in the %initial-action

scan-code.l is already passing argument to b4_dollar_dollar for the
initial acton, but its definition (of b4_dollar_dollar) does not use
this argument.

Generalize this definition, and use it for the %initial-action too.

* data/c.m4 (b4_dollar_dollar_, b4_dollar_pushdef, b4_dollar_popdef):
Instead of expecting a pointer, require a value, and use ".".
Since they are now generic enough, move to...
* data/c-like.m4: this new file.
* data/c.m4, data/java.m4: Load it.
* data/glr.c, data/lalr1.cc, data/lalr1.java, data/yacc.c: Use
b4_dollar_pushdef for the %initial-action.
* tests/actions.at: Check that.
* data/Makefile.am: Adjust.
* NEWS, doc/bison.texi: Document.

data/glr.c

@@ -2302,12 +2302,10 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
 #endif
 ])
 m4_ifdef([b4_initial_action], [
-m4_pushdef([b4_at_dollar],     [yylloc])dnl
-m4_pushdef([b4_dollar_dollar], [yylval])dnl
-  /* User initialization code.  */
-  b4_user_initial_action
-m4_popdef([b4_dollar_dollar])dnl
-m4_popdef([b4_at_dollar])])dnl
+b4_dollar_pushdef([yylval], [], [yylloc])dnl
+/* User initialization code.  */
+b4_user_initial_action
+b4_dollar_popdef])[]dnl
 [
   if (! yyinitGLRStack (yystackp, YYINITDEPTH))
     goto yyexhaustedlab;