.gitattribute: do not diff c_src and parser generated files

This should have been done years ago!

Signed-off-by: Jean Privat <jean@pryen.org>
lib: AbstractSorter accepts null

There is no real reason to refuse it.

Signed-off-by: Jean Privat <jean@pryen.org>
lib: remove REQUIRE on pipeline::sort_with

The AbstractSorter does all the job.

Signed-off-by: Jean Privat <jean@pryen.org>
src: use split_with instead of split

Signed-off-by: Jean Privat <jean@pryen.org>
src: change API of split and depreciate split_with

Signed-off-by: Jean Privat <jean@pryen.org>
tests: less regression tests (disable most nitg variants)

Signed-off-by: Jean Privat <jean@pryen.org>
test: new script testall.sh

test most engines easily.

Signed-off-by: Jean Privat <jean@pryen.org>