live555: fix invalid conversion error

live555: fix invalid conversion error

../../../modules/access/live555.cpp:2154:64: error: invalid conversion from 'char const*' to 'char*' [-fpermissive]
../../../contrib/arm-linux-androideabi/include/Base64.hh:28:16: error:   initializing argument 1 of 'unsigned char* base64Decode(char*, unsigned int&, Boolean)' [-fpermissive]

base64Decode appears to be defined as unsigned char* base64Decode(char* in, unsigned& resultSize, Boolean trimTrailingZeros);

Signed-off-by: Sébastien Escudier <sebastien-devel@celeos.eu>