tests: Split images -> tests/data + tests/guests
syntax-check: exempt *.pod from no-trailing-blank prohibition * .x-sc_trailing_blank: Exempt *.pod.
build: remove trailing blanks, enable syntax-check * regressions/test-cancellation-download-librarycancels.sh: * src/generator.ml: * cfg.mk (disable_temporarily): Remove sc_trailing_blank. * .x-sc_trailing_blank: New file.