sgemm(3) on Linux

The text d3b7370bb789, as Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze), Debian 5.0 (Lenny), Debian 4.0 (Etch) shipped it.

perform one of the matrix-matrix operations C := alpha*op( A )*op( B ) + beta*C,