librustc: Remove pub extern and priv extern from the language.

Place `pub` or `priv` on individual items instead.

src/test/compile-fail/foreign-unsafe-fn-called.rs

@@ -12,7 +12,7 @@
 
 mod test {
     #[abi = "cdecl"]
-    pub extern {
+    extern {
         pub unsafe fn free();
     }
 }

src/test/compile-fail/lint-unused-unsafe.rs

@@ -13,7 +13,7 @@
 #[deny(unused_unsafe)];
 
 mod foo {
-    pub extern {
+    extern {
         pub fn bar();
     }
 }

src/test/compile-fail/warn-foreign-int-types.rs

@@ -10,7 +10,7 @@
 
 //error-pattern:libc::c_int or libc::c_long should be used
 mod xx {
-    pub extern {
+    extern {
         pub fn strlen(str: *u8) -> uint;
         pub fn foo(x: int, y: uint);
     }