fix for radiotapdecap/encap

Because of the last commit for this file, the decapsulation for radiotap didn't work. it seems that linux is currently not doing radiotap header field aligning.

this patch adds a parameter to enabled/disable the aligning. default is still aligning header fields.

in radiotapencap the header length is wrong. one byte is missing. this leads to unrecognized wifi frames and wireshark shows an error (the data was ok, but the length field was not correct).