Generic memcpy should define MEMCOPY before including bcopy.c

Signed-off-by: Chris Dearman <chris@mips.com>

libc/string/memcpy.c

@@ -25,5 +25,5 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#define MEM_COPY
+#define MEMCOPY
 #include "bcopy.c"