Corrected LCD only error

If only an LCD is defined and no menu or keyboard defined, there is a
compilation error.

Added conditional compilation.

Marlin/BlinkM.h

@@ -0,0 +1,14 @@
+/*
+  BlinkM.h
+  Library header file for BlinkM library
+ */
+#if (ARDUINO >= 100)
+  # include "Arduino.h"
+#else
+  # include "WProgram.h"
+#endif
+
+#include "Wire.h"
+
+void SendColors(byte red, byte grn, byte blu);
+