replace stale sp objects

[andysouth]

Initially use rebuilt objects from here :
http://spatial.nhh.no/R/rebuilt_sp_objects/rworldmap/

Following email from CRAN :

CRAN@r-project.org 24 Aug 2020

Your package rworldmap stores data objects using classes defined
in the sp package or inheriting from those classes. From sp 1.4-* and
rgdal 1.5-*, CRS objects are now expected to have a comment containing
an WKT2 CRS representation - see:

https://www.r-spatial.org/r/2020/03/17/wkt.html

A section at the foot of

https://rgdal.r-forge.r-project.org/articles/CRS_projections_transformations.html#rebuilding-crs-objects

describes possible steps for updating CRS objects; earlier sections cover
background issues. Working around sp objects with stale CRS is already
causing difficulties, so your cooperation in upgrading will be helpful.An attempt has been made to rebuild data objects using sp::rebuild_CRS(),
and output (re-stored as version 2) may be found on my server at:

http://spatial.nhh.no/R/rebuilt_sp_objects/

The functions used are from the development version of rgdal, 1.5-17,
rev >= 1053, use:

install.packages("rgdal", repos="http://R-Forge.R-project.org")

and:

remotes::install_github("rsbivand/sp")

should you wish to make changes. Please check carefully that these objects
are as you would expect. Note that the rebuilt CRS object contains
a revised version of the input Proj4 string as well as the WKT2 string,
and may be used with both older and newer versions of sp. Objects
inheriting from sp classes but with NA CRS are not modified.

The objects found that could be rebuilt were as follows, with the file name
and object name separated by an underscore:

rworldmap/data/gridExData.rda_gridExData
rworldmap/data/countriesCoarseLessIslands.rda_countriesCoarseLessIslands
rworldmap/data/countriesCoarse.rda_countriesCoarse
rworldmap/data/coastsCoarse.rda_coastsCoarse
rworldmap/data/gridCountriesDegreesHalf.rda_gridCountriesDegreesHalf
rworldmap/data/gridCountriesNumeric.rda_gridCountriesNumeric
rworldmap/data/countriesLow.rda_countriesLow