Ensure that port reads do not block indefinitely if a user enters an incorrect timeout value (<100) on Linux or Mac.

src/main/java/com/fazecast/jSerialComm/SerialPort.java

@@ -657,6 +657,8 @@ public final class SerialPort
 			readTimeout = newReadTimeout;
 			writeTimeout = newWriteTimeout;
 		}
+		else if ((newReadTimeout > 0) && (newReadTimeout <= 100))
+			readTimeout = 100;
 		else
 			readTimeout = Math.round((float)newReadTimeout / 100.0f) * 100;