build: error out on -Wimplicit
These warnings are easy to miss during development:
../edid.c: In function ‘_di_edid_parse’:
../edid.c:254:25: warning: implicit declaration of function ‘di_edid_destroy’? [-Wimplicit-function-declaration]
254 | di_edid_destroy(edid);
| ^~~~~~~~~~~~~~~
And when missed, the code still compiles. Which means one needs to clean-build to show them again.
If it were only on me, I'd enable -Werror
for all warnings by default. But IIRC some people are against this...