split_string() System.f95 eats up delimiters

[albapa]

We call split_string in teach_sparse.f95:
call split_string(descriptor_str,':','{}',main_teach_sparse%descriptor_str(:),main_teach_sparse%n_coordinate,matching=.true.)

This finds the delimiters correctly (i.e. it will not consider other ":"-s nested in descriptors as delimiters), but in the process it removes nested "{}"-s, within the correctly found fields. That causes problems later, when other parts of the code try to interpret the fields.