Mark core gems with mrbgem tag

mrbgems/mruby-struct/src/struct.c

@@ -739,26 +739,28 @@ mrb_struct_values_at(mrb_state *mrb, mrb_value self)
 
   return mrb_get_values_at(mrb, self, RSTRUCT_LEN(self), argc, argv, struct_aref_int);
 }
-
-/*
- *  A <code>Struct</code> is a convenient way to bundle a number of
- *  attributes together, using accessor methods, without having to write
- *  an explicit class.
- *
- *  The <code>Struct</code> class is a generator of specific classes,
- *  each one of which is defined to hold a set of variables and their
- *  accessors. In these examples, we'll call the generated class
- *  "<i>Customer</i>Class," and we'll show an example instance of that
- *  class as "<i>Customer</i>Inst."
- *
- *  In the descriptions that follow, the parameter <i>symbol</i> refers
- *  to a symbol, which is either a quoted string or a
- *  <code>Symbol</code> (such as <code>:name</code>).
- */
 void
 mrb_mruby_struct_gem_init(mrb_state* mrb)
 {
   struct RClass *st;
+
+  /*
+   *  A <code>Struct</code> is a convenient way to bundle a number of
+   *  attributes together, using accessor methods, without having to write
+   *  an explicit class.
+   *
+   *  The <code>Struct</code> class is a generator of specific classes,
+   *  each one of which is defined to hold a set of variables and their
+   *  accessors. In these examples, we'll call the generated class
+   *  "<i>Customer</i>Class," and we'll show an example instance of that
+   *  class as "<i>Customer</i>Inst."
+   *
+   *  In the descriptions that follow, the parameter <i>symbol</i> refers
+   *  to a symbol, which is either a quoted string or a
+   *  <code>Symbol</code> (such as <code>:name</code>).
+   *
+   * @mrbgem mruby-struct
+   */
   st = mrb_define_class(mrb, "Struct",  mrb->object_class);
 
   mrb_define_class_method(mrb, st, "new",             mrb_struct_s_def,       MRB_ARGS_ANY());  /* 15.2.18.3.1  */