Enable typestate_check

Enable typestate checking (just for uninitialized vars) and un-XFAIL the
relevant tests for stage0.

src/test/compile-fail/break-uninit.rs

@@ -1,5 +1,4 @@
 // xfail-boot
-// xfail-stage0
 // error-pattern:Unsatisfied precondition
 
 fn foo() -> int {

src/test/compile-fail/break-uninit2.rs

@@ -1,5 +1,4 @@
 // xfail-boot
-// xfail-stage0
 // error-pattern:Unsatisfied precondition
 
 fn foo() -> int {

src/test/compile-fail/fru-typestate.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // -*- rust -*-
 
 // error-pattern: precondition

src/test/compile-fail/return-uninit.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern: precondition constraint
 
 fn f() -> int {

src/test/compile-fail/use-uninit-2.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern:Unsatisfied precondition
 
 fn foo(int x) {

src/test/compile-fail/use-uninit-3.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern:Unsatisfied precondition
 
 fn foo(int x) {

src/test/compile-fail/use-uninit-dtor.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern:Unsatisfied precondition
 
 fn main() {

src/test/compile-fail/use-uninit.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern:Unsatisfied precondition
 
 fn foo(int x) {

src/test/compile-fail/while-bypass.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern: precondition constraint
 
 fn f() -> int {

src/test/compile-fail/while-expr.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern: precondition constraint
 
 fn main() {

src/test/compile-fail/writing-through-uninit-vec.rs

@@ -1,4 +1,3 @@
-// xfail-stage0
 // error-pattern: Unsatisfied precondition constraint
 
 fn test() {