RQ decomposition using Givens rotations

Calculates RQ decomposition of A = RQ (3x3)

rqGivens Calculates RQ decomposition of A = RQ
Syntax:
[R, Q] = rqGivens(A);

Input:
A - 3-by-3 matrix of rank 3

Output:
R - Upper triangular matrix (3-by-3)
Q - Orthogonal matrix (3-by-3)

Description:
This function calculates the 3-dimensional RQ decomposition of A using
Givens rotations (equal to Euler rotations) Gx, Gy Gz:

Gx = [ 1 0 0;
0 c -s;
0 s c];

Gy = [ c 0 s;
0 1 0;
-s 0 c];

Gz = [ c -s 0;
s c 0;
0 0 1];

Ax = A * Gx to set Ax(3,2) to zero.
Axy = Ax * Gy to set Axy(3,1) to zero.
R = Axyz = Axy * Gz to set Axyz(2,1) to zero.

R = A * Gx * Gy * Gz
-> R * Gz' * Gy' * Gx' = A
-> Q = Gz' * Gy' * Gx'

See also:
- https://en.wikipedia.org/wiki/Givens_rotation#Dimension_3
- Hartley, Zisserman - Multiple View Geometry in Computer Vision
http://www.amazon.com/dp/0521540518 (Appendix 4, A4.1.1, page 579)