linker: implement shared namespaces

Shared namespaces clone the list of loaded native
libraries from the caller namespace. This allows
classloaders for bundled apps to share already loaded
libraries with default namespace.

Bug: http://b/22548808
Bug: http://b/26165097
Change-Id: I8949d45937fdb38e1f586ff0679003adac0d9dad
(cherry picked from commit e78deef364d952dd1141a2f3067a12060aaf11e6)

libdl/libdl.c

@@ -65,7 +65,7 @@ bool android_init_namespaces(const char* public_ns_sonames __unused,
 struct android_namespace_t* android_create_namespace(const char* name __unused,
                                                      const char* ld_library_path __unused,
                                                      const char* default_library_path __unused,
-                                                     bool isolated __unused,
+                                                     uint64_t type __unused,
                                                      const char* permitted_when_isolated_path __unused) {
   return 0;
 }