Always include <errno.h> instead of <sys/errno.h>

Always include <errno.h> instead of <sys/errno.h>

Including <sys/errno.h> instead of <errno.h> raises a compiler warning
when building against musl libc.  Always include <errno.h> instead of
<sys/errno.h> to prevent that compilation warning from being triggered
and to achieve consistency in this regard across the entire source tree.

(cherry picked from commit b5cd146033a5a269cae5784ef64d7045fa9f487c)