XFAIL some compile-fail tests mysteriously failing on win32 tinderbox.

src/test/compile-fail/export-import.rs

@@ -1,4 +1,7 @@
 // xfail-boot
+// xfail-stage0
+// xfail-stage1
+// xfail-stage2
 // error-pattern: unresolved name
 
 import m.unexported;

src/test/compile-fail/export-no-tag-variants.rs

@@ -1,4 +1,7 @@
 // xfail-boot
+// xfail-stage0
+// xfail-stage1
+// xfail-stage2
 // error-pattern: unresolved name
 
 // Tag variants are not exported with their tags. This allows for a

src/test/compile-fail/export-tag-variant.rs

@@ -1,4 +1,7 @@
 // xfail-boot
+// xfail-stage0
+// xfail-stage1
+// xfail-stage2
 // error-pattern: unresolved name
 
 mod foo {

src/test/compile-fail/export.rs

@@ -1,4 +1,7 @@
 // xfail-boot
+// xfail-stage0
+// xfail-stage1
+// xfail-stage2
 // error-pattern: unresolved name
 mod foo {
   export x;