SYM_AUTOCORR Autocorrelation of a symbolic vector
[V, VCORR] = SYM_AUTOCORR(SEQLEN), where SEQLEN>=1 is the length of the
sequence whose autocorrelation is to be calculated. V is a symbolic
vector of length SEQLEN that the function constructs and VCORR is the
symbolic autocorrelation vector.
The autocorrelation is calculated by first constructing the outer
product matrix and then summing over each diagonal.