run rustfmt on liballoc_jemalloc folder

src/liballoc_jemalloc/lib.rs

@@ -39,12 +39,12 @@ use libc::{c_int, c_void, size_t};
                not(target_env = "musl")),
            link(name = "pthread"))]
 #[cfg(not(cargobuild))]
-extern {}
+extern "C" {}
 
 // Note that the symbols here are prefixed by default on OSX and Windows (we
 // don't explicitly request it), and on Android and DragonFly we explicitly
 // request it as unprefixing cause segfaults (mismatches in allocators).
-extern {
+extern "C" {
     #[cfg_attr(any(target_os = "macos", target_os = "android", target_os = "ios",
                    target_os = "dragonfly", target_os = "windows"),
                link_name = "je_mallocx")]
@@ -136,8 +136,9 @@ pub extern "C" fn __rust_usable_size(size: usize, align: usize) -> usize {
 // are available.
 #[no_mangle]
 #[cfg(target_os = "android")]
-pub extern fn pthread_atfork(_prefork: *mut u8,
-                             _postfork_parent: *mut u8,
-                             _postfork_child: *mut u8) -> i32 {
+pub extern "C" fn pthread_atfork(_prefork: *mut u8,
+                                 _postfork_parent: *mut u8,
+                                 _postfork_child: *mut u8)
+                                 -> i32 {
     0
 }