fixed prototype: g++ will complain about definition not being a prototype,...

fixed prototype: g++ will complain about definition not being a prototype, should work with GCC and VC as well

include/mruby.h

@@ -147,7 +147,7 @@ mrb_obj_value(void *p)
 }
 
 static inline mrb_value
-mrb_false_value()
+mrb_false_value(void)
 {
   mrb_value v;
 
@@ -157,7 +157,7 @@ mrb_false_value()
 }
 
 static inline mrb_value
-mrb_nil_value()
+mrb_nil_value(void)
 {
   mrb_value v;
 
@@ -167,7 +167,7 @@ mrb_nil_value()
 }
 
 static inline mrb_value
-mrb_true_value()
+mrb_true_value(void)
 {
   mrb_value v;
 
@@ -177,7 +177,7 @@ mrb_true_value()
 }
 
 static inline mrb_value
-mrb_undef_value()
+mrb_undef_value(void)
 {
   mrb_value v;
 

include/mruby/variable.h

@@ -14,8 +14,8 @@ extern "C" {
 typedef struct global_variable {
     int   counter;
     mrb_value *data;
-    mrb_value (*getter)();
-    void  (*setter)();
+    mrb_value (*getter)(void);
+    void  (*setter)(void);
     //void  (*marker)();
     //int block_trace;
     //struct trace_var *trace;