Add API for freeing thread_local state

base/runtime/thread_management.odin

@@ -0,0 +1,34 @@
+package runtime
+
+Thread_Local_Cleaner :: #type proc "odin" ()
+
+@(private="file")
+thread_local_cleaners: [8]Thread_Local_Cleaner
+
+// Add a procedure that will be run at the end of a thread for the purpose of
+// deallocating state marked as `thread_local`.
+//
+// Intended to be called in an `init` procedure of a package with
+// dynamically-allocated memory that is stored in `thread_local` variables.
+add_thread_local_cleaner :: proc "contextless" (p: Thread_Local_Cleaner) {
+	for &v in thread_local_cleaners {
+		if v == nil {
+			v = p
+			return
+		}
+	}
+	panic_contextless("There are no more thread-local cleaner slots available.")
+}
+
+// Run all of the thread-local cleaner procedures.
+//
+// Intended to be called by the internals of a threading API at the end of a
+// thread's lifetime.
+run_thread_local_cleaners :: proc "odin" () {
+	for p in thread_local_cleaners {
+		if p == nil {
+			break
+		}
+		p()
+	}
+}