Create a buffer overflow test.

This tests buffer overflow for the basic types. It does not currently
test the platform int and uint until the final function definitions
are determined.

src/endian.rs

@@ -36,7 +36,7 @@ macro_rules! read_bytes
    ({
       use std::$return_type;
 
-      assert!($return_type::BYTES <= $buffer.len());
+      assert!($buffer.len() < $return_type::BYTES);
       unsafe
       {
          (*($buffer.as_ptr() as *const $return_type)).$convert_func()
@@ -52,7 +52,7 @@ macro_rules! write_bytes
    ({
       use std::$value_type;
 
-      assert!($value_type::BYTES <= $buffer.len());
+      assert!($buffer.len() < $value_type::BYTES);
       unsafe
       {
          let size: usize;