* Fix spelling/wording issues
* gitlab CI: add a basic build test
* gitlab CI: stop requiring Signed-off-by in commits
* Mark help(), usage(), and grammar() with _X_NORETURN _X_COLD
* Declare help() and print_help() as static
* Rename "dpy" function arguments to "display" to avoid shadowing global
* Resolve many gcc -Wsign-compare warnings
* Variable scope reductions as suggested by cppcheck
OBS-URL: https://build.opensuse.org/package/show/X11:XOrg/xprop?expand=0&rev=15
