Fix some -Wextra warnings
Mostly -Wsign-compare warning and -Wold-style-decl
changeset in conversion.c and type-u32.c
may need attention.
If it's OK maybe adding add_project_arguments('-Wextra', language : 'c')
to prevent future warning while developping.
Also I have some stashed change about main args not used if it's worth it.
(Doing this work before trying gcc' -fanalyzer on gimp+babl)
Edited by darnuria