Remove ";" suffix from function-type macros.

Function-type macro should not end with ";".

In the current implementation, the following source code occurs compilation error,
because the definition of `mrb_gc_mark_value` ends with ";".
```c
if (a)
  mrb_gc_mark_value(mrb,val1);
else
  mrb_gc_mark_value(mrb,val2);
```