Test regression from 1.10 to 1.11

[mattwigway]

On master, all tests pass on 1.10, but starting in 1.11 the "Simple Tutorial" tests fail trying to access the result array after running the bounds the operations:

Simple Tutorial: Error During Test at /Users/mwbc/.julia/dev/LibSpatialIndex/test/runtests.jl:43
  Test threw exception
  Expression: isapprox(pmaxs, [0.5, 0.5])
  BoundsError: attempt to access MemoryRef{Float64} at index [1]

I suspect this has to do with the changes to the structure of Vector in 1.11. There's some pointer double-indirection happening on the C side (the input value is a double**, i.e. pointer to a pointer to a double, and the C code modifies the second pointer to point at a new location). This seems like it shouldn't work at all given that it appears julia is treating this as a double* rather than a double**, but seems to work in 1.10 and even works from the REPL in 1.12, but not in testing.

[asinghvi17]

Fixed in #39