* gitlab CI: stop requiring Signed-off-by in commits
* Print which arguments were unknown before giving usage message
* Add -help and -version options
* Clear 9 -Wuseless-cast warnings
* Fix -Wshadow warning for Display argument to Error()
* Fix -Wself-assign warning from clang 13
* Fix -Wmissing-variable-declarations warning from clang 13
* usage: add noreturn attribute
* Quiet 64 -Wunused-parameter warnings from clang 13
* Use double for all floating point numbers, not a mix of double and float
OBS-URL: https://build.opensuse.org/package/show/X11:XOrg/xmag?expand=0&rev=13
