[Rd] Survival package (was Building R-patched and R-devel fails)

[Therneau, Terry M., Ph.D.]

Just a note FYI:  The survival package can now create predicted "probability in state" 
curves from a multi-state model, and that computation uses the exponential of a matrix.

Hence the new NAMESPACE line of "importFrom(Matrix, expm)", and the resulting dependency 
of 'survival' on 'Matrix'.  It is the only part of the package used.

Terry T.