Refactor ptrace_get_data

The boxing and unboxing was unnecessary and instead the references to the type on
the stack can just be cast.

src/sys/ptrace.rs

@@ -97,13 +97,10 @@ fn ptrace_peek(request: ptrace::PtraceRequest, pid: Pid, addr: *mut c_void, data
 /// requests.
 fn ptrace_get_data<T>(request: ptrace::PtraceRequest, pid: Pid) -> Result<T> {
     // Creates an uninitialized pointer to store result in
-    let data: Box<T> = Box::new(unsafe { mem::uninitialized() });
-    let data: *mut c_void = unsafe { mem::transmute(data) };
-    let res = unsafe { ffi::ptrace(request, pid.into(), ptr::null_mut(), data) };
+    let data: T = unsafe { mem::uninitialized() };
+    let res = unsafe { ffi::ptrace(request, pid.into(), ptr::null_mut(), &data as *const _ as *const c_void) };
     Errno::result(res)?;
-    // Convert back into the original data format and return unboxed value
-    let data: Box<T> = unsafe { mem::transmute(data) };
-    Ok(*data)
+    Ok(data)
 }
 
 fn ptrace_other(request: ptrace::PtraceRequest, pid: Pid, addr: *mut c_void, data: *mut c_void) -> Result<c_long> {