Print "ovf" if float to be printed doesn't fit in a long.

http://code.google.com/p/arduino/issues/detail?id=967

Author: damellis

hardware/arduino/cores/arduino/Print.cpp

@@ -228,6 +228,8 @@ size_t Print::printFloat(double number, uint8_t digits)
 
   if (isnan(number)) return print("nan");
   if (isinf(number)) return print("inf");
+  if (number > 4294967040.0) return print ("ovf");  // constant determined empirically
+  if (number <-4294967040.0) return print ("ovf");  // constant determined empirically
 
   // Handle negative numbers
   if (number < 0.0)