opToepGauss Toeplitz matrix with Gaussian entries.
OP = opToepGauss(M,N,TYPE,NORMALIZED) creates an M by N Toeplitz
matrix with Gaussian entries. TYPE can either be 'toeplitz' or
'circular'. For the 'toeplitz' type matrix, m+n-1 different
generating entries are generated at random, whereas for the
'circular' matrix, only max(m,n) are needed. When the TYPE field
is empty , or not specified 'toeplitz' is chosen by
default. Setting the NORMALIZED flag scales the columns of the
Toeplitz matrix to unit norm. Multiplication is implemented using
the fast Fourier transform. The use of such matrices in compressed
sensing was suggested by:
 W. U. Bajwa, J. D. Haupt, G. M. Raz, S. J. Wright, and
R. D. Nowak, Toeplitz-Structured Compressed Sensing Matrices,
IEEE/SP 14th Workshop on Statistical Signal Processing,
pp. 294-298, August 2007.