move prototype of mrb_format() from error.h to mruby.h; ref #2274

include/mruby.h

@@ -422,6 +422,8 @@ void* mrb_alloca(mrb_state *mrb, size_t);
 #define mrb_assert_int_fit(t1,n,t2,max) ((void)0)
 #endif
 
+mrb_value mrb_format(mrb_state *mrb, const char *format, ...);
+
 #if defined(__cplusplus)
 }  /* extern "C" { */
 #endif

include/mruby/error.h

@@ -15,7 +15,6 @@ void mrb_sys_fail(mrb_state *mrb, const char *mesg);
 mrb_value mrb_exc_new_str(mrb_state *mrb, struct RClass* c, mrb_value str);
 #define mrb_exc_new_str_lit(mrb, c, lit) mrb_exc_new_str(mrb, c, mrb_str_new_lit(mrb, lit))
 mrb_value mrb_make_exception(mrb_state *mrb, int argc, const mrb_value *argv);
-mrb_value mrb_format(mrb_state *mrb, const char *format, ...);
 void mrb_exc_print(mrb_state *mrb, struct RObject *exc);
 void mrb_print_backtrace(mrb_state *mrb);
 mrb_value mrb_exc_backtrace(mrb_state *mrb, mrb_value exc);