AAC config parser fix

[shurkaxaa]

Sometimes AAC fmtp.parameters.config much more than expected by the existing parser UInt16.
As a result, playback failed with error - RangeError: "value" argument is out of bounds.
It seems fmtp.parameters.config can contain more bytes than expected by this library.
For example for this stream - rtsp://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mp4.
Media information below.
And exactly the first four bytes contain proper - audio object type, frequency, etc...

              {                                                                                               
                "bandwidth": "128",                                                                           
                "bwtype": "AS",                                                                               
                "control": "trackID=1",                                                                       
                "fmt": 97,                                                                                    
                "fmtp": {                                                                                     
                    "format": "97",                                                                           
                    "parameters": {                                                                           
                        "config": "121056E500",                                                               
                        "indexdeltalength": "3",                                                              
                        "indexlength": "3",                                                                   
                        "mode": "AAC-hbr",                                                                    
                        "profile-level-id": "1",                                                              
                        "sizelength": "13"                                                                    
                    }                                                                                         
                },                                                                                            
                "port": 0,                                                                                    
                "protocol": "RTP/AVP",                                                                        
                "rtpmap": {                                                                                   
                    "clockrate": 44100,                                                                       
                    "encodingName": "MPEG4-GENERIC",                                                          
                    "encodingParameters": "2",                                                                
                    "payloadType": 97                                                                         
                },                                                                                            
                "type": "audio"                                                                               
            }                                                                                                 

[steabert]

This should be OK provided we know why it's only the first 4 characters?