According to RFC 1123 [1], hostnames can start with a digit too.

[1] http://tools.ietf.org/html/rfc1123#page-13



Signed-off-by: Ján Tomko <jtomko@redhat.com>
Cc: qemu-stable@nongnu.org
[Use strspn, not strcspn. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>