Add a test for rust-lang#1914 and rust-lang#1915

Author: topecongiro

tests/source/issue-1914.rs

@@ -0,0 +1,6 @@
+// rustfmt-max_width: 80
+
+extern "C" {
+#[link_name = "_ZN7MyClass26example_check_no_collisionE"]
+    pub static mut  MyClass_example_check_no_collision  :  * const :: std :: os :: raw :: c_int ;
+}

tests/target/issue-1914.rs

@@ -0,0 +1,7 @@
+// rustfmt-max_width: 80
+
+extern "C" {
+    #[link_name = "_ZN7MyClass26example_check_no_collisionE"]
+    pub static mut MyClass_example_check_no_collision:
+        *const ::std::os::raw::c_int;
+}