[Rd] Suppressing a warning from library()

[Terry Therneau]

I get a warning about "1 warning message" using R CMD check on the
survival library.  It comes from the code snippet:

   if (library(cmprsk, logical.return=TRUE)) {
	# further test of competing risks from survfit
	.
	.
	}
This is a very useful additional test when I'm checking any changes to
the affected code, so I like having this in my test suite even though it
doesn't run automatically.  

This argues for a change in library -- when the user sets logical.return
=T they don't need a warning message too.  I submit this to the R core
and their collective wisdom.

I admit that mine is an unusual case, and for now I'll turn if off with
options(warn=-1) 

Terry T.