eliminate os_core, move into base; eliminate regs, move into arch abstraction layer, define x64 regs in x64 layer; move win32 backend for os core (now base) functionality to top-level win32 layer

src/base/base_dynamic_libraries.h

@@ -0,0 +1,20 @@
+// Copyright (c) Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+#ifndef BASE_DYNAMIC_LIBARIES_H
+#define BASE_DYNAMIC_LIBARIES_H
+
+typedef struct Library Library;
+struct Library
+{
+  U64 u64[1];
+};
+
+////////////////////////////////
+//~ rjf: @per_os_impl Dynamically-Loaded Libraries
+
+internal Library library_open(String8 path);
+internal void library_close(Library lib);
+internal VoidProc *library_load_proc(Library lib, String8 name);
+
+#endif // BASE_DYNAMIC_LIBARIES_H