**The result of A**B is defined as follows when A is a
square matrix and B is an integer scalar:
B > 0, A**B is A*…*A, where there are
B ‘A’s. (PSPP implements this efficiently for large
B, using exponentiation by squaring.)
B < 0, A**B is INV(A**(-B)).
B = 0, A**B is the identity matrix.
PSPP reports an error if A is not square or B is not
an integer.
Examples:
{2, 5; 1, 4}**3 | ⇒ | {48, 165; 33, 114} |
{2, 5; 1, 4}**0 | ⇒ | {1, 0; 0, 1} |
10*{4, 7; 2, 6}**-1 | ⇒ | {6, -7; -2, 4} |