Added variable inits to copy_avrdude.py to fix windows error

While attempting to use the copy_avrdude.py script on my Windows 7 x64 environment, using Cygwin and Python 2.7.3, I ran into the following error:

```sh
Traceback (most recent call last):
  File "copy_avrdude.py", line 49, in <module>
    if not os.path.isfile(os.path.join(path_to_firmware, avrdude_name)):
NameError: name 'avrdude_name' is not defined
```
And later this error:
```sh
Copying avrdude files into /home/okeefm/s3g/makerbot_driver/Firmware
Traceback (most recent call last):
  File "copy_avrdude.py", line 51, in <module>
    for file in files:
NameError: name 'files' is not defined

```
These errors were solved by defining `avrdude_name`, `platform_folder` (for completeness) and `files` before parsing the argument values and checking the platform type.