Fix config file parsing on musl libc
Fix config file parsing on musl libc

On the musl libc, autorun, layout and workspace name settings were
always rejected as invalid. As it turns out, parsing those was relying
on sscanf incorrectly matching %Nc as long as there is at least one
character. This is fixed by matching only the initial part of the string
via sscanf and skipping ahead by the amount of bytes consumed. This also
avoids unnecessary zeroing, copying and possible implicit truncation.

Relevant glibc bug:
https://sourceware.org/bugzilla/show_bug.cgi?id=12701

conformal/spectrwm,conformal/spectrwm,conformal/spectrwm