Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/wasi-common/src/sys/unix/linux/osfile.rs

@@ -0,0 +1,32 @@
+use std::fs;
+use std::ops::{Deref, DerefMut};
+use std::os::unix::prelude::{AsRawFd, RawFd};
+
+#[derive(Debug)]
+pub(crate) struct OsFile(fs::File);
+
+impl From<fs::File> for OsFile {
+    fn from(file: fs::File) -> Self {
+        Self(file)
+    }
+}
+
+impl AsRawFd for OsFile {
+    fn as_raw_fd(&self) -> RawFd {
+        self.0.as_raw_fd()
+    }
+}
+
+impl Deref for OsFile {
+    type Target = fs::File;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for OsFile {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}