message: Fix i8 ptr instead of c_char ptr passed to OSRImportFromESRI()
  c_char is not set to i8 on every architecture, and indeed, this fixes
  the build on arm64 and possibly other architectures as well.
diff: use crate::utils::{_last_cpl_err, _last_null_pointer_err, _string};
  use gdal_sys::{self, CPLErr, OGRCoordinateTransformationH, OGRErr, OGRSpatialReferenceH};
  -use libc::c_int;
  +use libc::{c_int, c_char};
  use std::ffi::{CStr, CString};
  use std::ptr;
  use std::str::FromStr;
  @@ -166,7 +166,7 @@ impl SpatialRef {
  pub fn from_esri(esri_wkt: &str) -> Result<SpatialRef> {
  let c_str = CString::new(esri_wkt)?;
  - let mut ptrs = vec![c_str.as_ptr() as *mut i8, ptr::null_mut()];
  + let mut ptrs = vec![c_str.as_ptr() as *mut c_char, ptr::null_mut()];
  let null_ptr = ptr::null_mut();
  let c_obj = unsafe { gdal_sys::OSRNewSpatialReference(null_ptr) };
  let rv = unsafe { gdal_sys::OSRImportFromESRI(c_obj, ptrs.as_mut_ptr()) };
  