maint: Syntax cleanup

* dietncl/filter/region.lua (apply): Likewise.
* dietncl/path.lua: Likewise.
* dietncl/xmlsugar.lua (domatch): Likewise.
* tests/test-filter-import.lua: Likewise.
* tests/test-init-parse-sample.ncl: Likewise.
* tests/test-xmlsugar-clone.lua: Likewise.
* tests/test-xmlsugar-equal.lua: Likewise.
tests: Simplify util.uequal code

* tests/util.lua (uequal): Likewise.
tests: Make filter.region tests stricter

* tests/test-filter-region.lua: Likewise.