qz
QZ decomposition of a pair of real matrices.
`(at, bt, Q, Z)=qz(a, b)`
 Inputs `a` A real square matrix. `b` A real square matrix of the same size as `a` . Outputs `at` A matrix of the same size as the inputs with zeros below the main sub-diagonal to the left of the main diagonal. `bt` A matrix of the same size as the inputs with zeros below the main sub-diagonal to the left of the main diagonal. `Q` A unitary matrix of the same size as the inputs. `Z` A unitary matrix of the same size as the inputs.

Description
The matrices `at` and `bt` are related to the inputs via the transformations `at=Q'*a*Z` and `bt=Q'*b*Z` .
Example
```>>a=[1 2 3;5 7 9; 13 12 15]
>>b=[12 19 23; 76 89 19; 12 16 31]
>>a
1          2          3
5          7          9
13         12         15

>>b
12         19         23
76         89         19
12         16         31

>>[at,bt,Q,Z]=qz(a,b)
>>at
-4.0413      22.6403      -8.0551
0       10.464      -1.9034
0            0       0.2838

>>bt
-3.1528      44.5148     -12.0142
0      78.1416     -85.2491
0            0      30.7185

>>at-Q'*a*Z
Scaled by 10^-13
0.0888      -0.9948       0.2842
-0.0422       0.7638      -0.1665
-0.1024       1.5123      -0.3331

>>bt-Q'*b*Z
Scaled by 10^-12
0.02      -0.6466       0.5365
0.0173       0.3411      -0.2984
-0.0058       0.8082      -0.6608

```