Add file scopes for the packages

core/os/os_windows.odin

@@ -1,7 +1,7 @@
 package os
 
 import "core:sys/win32"
-// import "core:mem"
+import "core:mem"
 
 Handle    :: distinct uintptr;
 File_Time :: distinct u64;

core/runtime/_preload.odin

@@ -1,7 +1,6 @@
 package runtime
 
 import "core:os"
-// import "core:fmt" // TODO(bill): Remove the need for `fmt` here
 import "core:unicode/utf8"
 import "core:raw"
 import "core:mem"