Use `clamp` to load invalid `LatLon` coordinates from files

[juliohm]

Sometimes datasets are shared invalid latitude:

load: Error During Test at /home/juliohm/.julia/dev/GeoIO/test/io/shapefile.jl:2
  Got exception outside of a @test
  ArgumentError: the latitude must be in the range [-90°,90°], while -90.00000000000003° was provided

We need to clamp the value in these cases.