Reading @ with GDAL is broken on Windows

[joa-quim]

grdinfo @warning.png
ERROR 4: `c:c:/j/.gmt/cache//j/.gmt/cache/warning.png' does not exist in the file system, and is not recognized as a supported dataset name.
grdinfo (gmtapi_import_grid): Not a supported grid format [c:/j/.gmt/cache/warning.png]

The problem is in

GMT_LOCAL GDALDatasetH gdal_open (struct GMT_CTRL *GMT, char *gdal_filename) {
	char *file = NULL, path[PATH_MAX] = {""}, *c = NULL;
	if (gmtlib_found_url_for_gdal (gdal_filename))	/* A vis*** URL, pass to GDAL as is */
		strncpy (path, gdal_filename, PATH_MAX-1);
	else if ((c = strchr(gdal_filename, ':'))) {		/* Assume it is a SUBDATASET */

: is not a SUBDATASET separator it's the c:

I knew that test was not good to have. So we still need a 6.1.1 soon.