Precision -- an optional argument

Functions with optional argument named Precision:

• intersect(RRi,RRi,Precision=>...) -- see intersect(RRi) -- intersection of input intervals
• interval(...,Precision=>...) -- see interval -- construct an interval
• rays(Matrix,Precision=>...) (missing documentation)
• roots(RingElement,Precision=>...) -- see roots(RingElement) -- compute the roots of a polynomial
• solve(...,Precision=>...) -- see solve -- solve linear equation(s)