fix #92

[bastistician]

spp is "SpatialPoints", so the proj4string argument is ignored anyway
(and produces a warning since 9101ce2)

[bastistician]

@edzer: Is there anything I can do to amplify this PR? It will fix #92.

With current sp, I'm getting a whole bunch of these warnings

  If the coords argument is a SpatialPoints object, set its CRS first;
  the proj4string argument to this function is ignored.

from calling spplot in surveillance.

[edzer]

I see this is caused by (indirect) contribution from @finnlindgren. If surveillance would have used this in a package test, reverse dependency checks should have caught it before release.

[bastistician]

Unfortunately not. Warnings from running tests and examples are currently not raised to the R CMD check log.
This is why I let my local "make check" rule additionally grep the generated -Ex.Rout file for "^Warning" (see HenrikBengtsson/Wishlist-for-R#83).

BTW, in released sp 1.4-4 itself, the example(spplot, ask=FALSE) also produces the above warning.
I see quiet a few other warnings in sp-Ex.Rout, but I haven't checked whether they are expected.