make init function consistent: mrb_init_symbols to mrb_init_symbol

src/init.c

@@ -8,7 +8,7 @@
 
 void mrb_init_class(mrb_state*);
 void mrb_init_symtbl(mrb_state*);
-void mrb_init_symbols(mrb_state*);
+void mrb_init_symbol(mrb_state*);
 void mrb_init_object(mrb_state*);
 void mrb_init_kernel(mrb_state*);
 void mrb_init_enumerable(mrb_state*);
@@ -42,7 +42,7 @@ mrb_init_core(mrb_state *mrb)
   mrb_init_comparable(mrb);
   mrb_init_enumerable(mrb);
 
-  mrb_init_symbols(mrb);
+  mrb_init_symbol(mrb);
   mrb_init_proc(mrb);
   mrb_init_string(mrb);
   mrb_init_array(mrb);

src/symbol.c

@@ -363,7 +363,7 @@ mrb_sym2name(mrb_state *mrb, mrb_sym sym)
 }
 
 void
-mrb_init_symbols(mrb_state *mrb)
+mrb_init_symbol(mrb_state *mrb)
 {
   struct RClass *sym;