Print "inf" for infinite floating point numbers (using isinf()).

http://code.google.com/p/arduino/issues/detail?id=961

hardware/arduino/cores/arduino/Print.cpp

@@ -227,6 +227,7 @@ size_t Print::printFloat(double number, uint8_t digits)
   size_t n = 0;
   
   if (isnan(number)) return print("nan");
+  if (isinf(number)) return print("inf");
   
   // Handle negative numbers
   if (number < 0.0)