allocator interface (first pass)

examples/programs/mem_allocator/main.bro

@@ -0,0 +1,20 @@
+mem :: import "@std/mem"
+
+main func() i32 {
+	memory ?*mut u8 = mem.alloc(mem.heap, 4, 1)
+	defer mem.free(mem.heap, memory, 4, 1)
+
+	if memory |bytes| {
+		bytes[0] = 10
+		bytes[1] = 20
+		bytes[2] = bytes[0] + bytes[1]
+
+		if (bytes[2] != 30) {
+			return 2
+		}
+
+		return 0
+	}
+
+	return 1
+}