introduce logging for debug purposes

xencall/examples/domain_create.rs

@@ -3,6 +3,8 @@ use xencall::sys::CreateDomain;
 use xencall::{XenCall, XenCallError};
 
 fn main() -> Result<(), XenCallError> {
+    env_logger::init();
+
     let call = XenCall::open()?;
     let domctl: DomainControl = DomainControl::new(&call);
     let domid = domctl.create_domain(CreateDomain::default())?;

xencall/examples/domain_info.rs

@@ -2,6 +2,8 @@ use xencall::domctl::DomainControl;
 use xencall::{XenCall, XenCallError};
 
 fn main() -> Result<(), XenCallError> {
+    env_logger::init();
+
     let call = XenCall::open()?;
     let domctl: DomainControl = DomainControl::new(&call);
     let info = domctl.get_domain_info(1)?;

xencall/examples/version_capabilities.rs

@@ -1,6 +1,8 @@
 use xencall::{XenCall, XenCallError};
 
 fn main() -> Result<(), XenCallError> {
+    env_logger::init();
+
     let call = XenCall::open()?;
     let info = call.get_version_capabilities()?;
     println!("{:?}", info);