h_cl - closed loop matrix
Given the standard plant P (with r=size(P22)) and the controller K, this function returns the closed loop matrix Acl.
The poles of Acl must be stable for the internal stability of the closed loop system.
Acl is the A-matrix of the linear system [I -P22;-K I]^-1 i.e. the A-matrix of lft(P,r,K)