cher2(3) on Linux

The text de4b66741e56, as Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch) shipped it.

perform the hermitian rank 2 operation A := alpha*x*conjg( y' ) + conjg( alpha )*y*conjg( x' ) + A,