Add a very simple test program

Not quite a unit test, it looks more like an example
but still something.

src/dynafunc_maker.cpp

@@ -100,6 +100,10 @@ namespace wren {
 		m_used_bytes = m_page_size;
 	}
 
+	std::size_t DynafuncMaker::total_memory() const {
+		return m_pages.size() * m_page_size;
+	}
+
 	unsigned char* DynafuncMaker::allocate_chunk() {
 		if (m_page_size - m_used_bytes < g_dynafunc_len) {
 			unique_ptr_free_t page(std::aligned_alloc(m_page_size, m_page_size));

src/dynafunc_maker.hpp

@@ -18,6 +18,7 @@
 #pragma once
 
 #include <vector>
+#include <cstddef>
 
 namespace wren {
 	class VM;
@@ -31,6 +32,8 @@ namespace wren {
 		void* make (VM* vm, foreign_method_t cb);
 		void clear() noexcept;
 
+		std::size_t total_memory() const;
+
 	private:
 		unsigned char* allocate_chunk();
 

src/vm.cpp

@@ -271,6 +271,10 @@ namespace wren {
 		return nullptr != m_local->user_data;
 	}
 
+	std::size_t VM::dynafunc_byte_size() const {
+		return m_local->dynafunc.total_memory();
+	}
+
 	void VM::ensure_slots (int num_slots) {
 		wrenEnsureSlots(m_local->wvm, num_slots);
 	}