Allow recursive static variables.

There isn't any particularly good reason for this restriction, so just
get rid of it, and fix trans to handle this case.

src/test/compile-fail/const-recursive.rs

@@ -8,9 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: recursive constant
-static a: isize = b;
-static b: isize = a;
+const a: isize = b; //~ ERROR recursive constant
+const b: isize = a; //~ ERROR recursive constant
 
 fn main() {
 }

src/test/compile-fail/issue-17252.rs

@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-static FOO: usize = FOO; //~ ERROR recursive constant
+const FOO: usize = FOO; //~ ERROR recursive constant
 
 fn main() {
     let _x: [u8; FOO]; // caused stack overflow prior to fix
     let _y: usize = 1 + {
-        static BAR: usize = BAR; //~ ERROR recursive constant
+        const BAR: usize = BAR; //~ ERROR recursive constant
         let _z: [u8; BAR]; // caused stack overflow prior to fix
         1
     };

src/test/run-pass/static-recursive.rs

@@ -0,0 +1,15 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+static mut S: *const u8 = unsafe { &S as *const *const u8 as *const u8 };
+
+pub fn main() {
+    unsafe { assert_eq!(S, *(S as *const *const u8)); }
+}