declaration shadows a local variable, in utf8.c

[snej]

There's a shadowed local variable in the function linenoiseUtf8NextCharLen. I build with -Wshadow and -Werror, so this warning breaks my build.

Behavior

Building with Clang ("Apple clang version 12.0.0") and -Wshadow produces:

linenoise-mob/utf8.c:468:13: error: declaration shadows a local variable [-Werror,-Wshadow]
        int cp;
            ^
linenoise-mob/utf8.c:459:9: note: previous declaration is here
    int cp;
        ^

Suggested Fix

Delete the duplicate int cp declaration, line 468: the existing cp in the outer scope isn't used again, so there's no harm in reusing it. Either that or rename the second cp to something unique.

(Apologies for not submitting a PR, but it didn't seem worth it to fork the entire repo just to submit a trivial 1-liner.)

Workaround

Update makefile / project to disable -Wshadow for this source file ... but it'd be better if the problem were fixed, since variable shadowing is kind of a footgun.