SOPGTR generates a real orthogonal matrix Q which is defined as the
 product of n-1 elementary reflectors H(i) of order n, as returned by
 SSPTRD using packed storage:

 if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),

 if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).

          UPLO is CHARACTER*1
          = 'U': Upper triangular packed storage used in previous
                 call to SSPTRD;
          = 'L': Lower triangular packed storage used in previous
                 call to SSPTRD.

          N is INTEGER
          The order of the matrix Q. N >= 0.

          AP is REAL array, dimension (N*(N+1)/2)
          The vectors which define the elementary reflectors, as
          returned by SSPTRD.

          TAU is REAL array, dimension (N-1)
          TAU(i) must contain the scalar factor of the elementary
          reflector H(i), as returned by SSPTRD.

          Q is REAL array, dimension (LDQ,N)
          The N-by-N orthogonal matrix Q.

          LDQ is INTEGER
          The leading dimension of the array Q. LDQ >= max(1,N).

          WORK is REAL array, dimension (N-1)

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value