* glom/libglom/utils.[h|cc]: Added get_temp_file_uri(),
get_temp_file_path(), get_temp_directory_uri() and
get_temp_directory_path(), using the correct awkward code that
avoids overwriting existing files.
* glom/application.cc:
* glom/libglom/connectionpool_backends/postgres_self.cc:
* glom/libglom/report_builder.cc:
* glom/utility_widgets/imageglom.cc:
* tests/import/utils.cc:
* tests/test_document_autosave.cc:
* tests/test_selfhosting_new_empty.cc:
* tests/test_selfhosting_utils.cc: Use these functions instead
of repeating the same stuff badly.
* Makefile_tests.am: Link to libglom so the import tests can use
the new utility functions.