Add raw address of expressions to the AST and HIR

src/librustc_error_codes/error_codes/E0745.md

@@ -0,0 +1,20 @@
+Cannot take address of temporary value.
+
+Erroneous code example:
+
+```compile_fail,E0745
+# #![feature(raw_ref_op)]
+fn temp_address() {
+    let ptr = &raw const 2;   // ERROR
+}
+```
+
+To avoid the error, first bind the temporary to a named local variable.
+
+```ignore
+# #![feature(raw_ref_op)]
+fn temp_address() {
+    let val = 2;
+    let ptr = &raw const val;
+}
+```