lartgs: generate plane rotation for bidiag SVD

Functions
subroutine	dlartgs (x, y, sigma, cs, sn)
	DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.
subroutine	slartgs (x, y, sigma, cs, sn)
	SLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.

Detailed Description