moved crates in lib/ to src/, renamed crates, modified some files' text (#660)

moved crates in lib/ to src/, renamed crates, modified some files' text (#660)

cranelift/codegen/meta/src/error.rs

@@ -0,0 +1,47 @@
+use std::fmt;
+use std::io;
+
+/// An error that occurred when the cranelift_codegen_meta crate was generating
+/// source files for the cranelift_codegen crate.
+#[derive(Debug)]
+pub struct Error {
+    inner: Box<ErrorInner>,
+}
+
+impl Error {
+    /// Create a new error object with the given message.
+    pub fn with_msg<S: Into<String>>(msg: S) -> Error {
+        Error {
+            inner: Box::new(ErrorInner::Msg(msg.into())),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.inner)
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(e: io::Error) -> Self {
+        Error {
+            inner: Box::new(ErrorInner::IoError(e)),
+        }
+    }
+}
+
+#[derive(Debug)]
+enum ErrorInner {
+    Msg(String),
+    IoError(io::Error),
+}
+
+impl fmt::Display for ErrorInner {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            ErrorInner::Msg(ref s) => write!(f, "{}", s),
+            ErrorInner::IoError(ref e) => write!(f, "{}", e),
+        }
+    }
+}