Move core:runtime to base:runtime; keep alias around

base/runtime/default_allocators_general.odin

@@ -0,0 +1,23 @@
+//+build !windows
+//+build !freestanding
+//+build !wasi
+//+build !js
+package runtime
+
+// TODO(bill): reimplement these procedures in the os_specific stuff
+import "core:os"
+
+when ODIN_DEFAULT_TO_NIL_ALLOCATOR {
+	_ :: os
+
+	// mem.nil_allocator reimplementation
+	default_allocator_proc :: nil_allocator_proc
+	default_allocator :: nil_allocator
+} else {
+
+	default_allocator_proc :: os.heap_allocator_proc
+
+	default_allocator :: proc() -> Allocator {
+		return os.heap_allocator()
+	}
+}