Split mojo_system dylib into public and private

mojo/system/memory.cc

Index: mojo/system/memory.cc
diff --git a/mojo/system/memory.cc b/mojo/system/memory.cc
index f20b61ddd546ef4833053bdbd69b9603080bb1e2..633b2bef4adb28f34e4c2129fe5d82835fce6e20 100644
--- a/mojo/system/memory.cc
+++ b/mojo/system/memory.cc
@@ -23,9 +23,9 @@ bool VerifyUserPointerForSize(const void* pointer, size_t count) {
 }
 
 // Explicitly instantiate the sizes we need. Add instantiations as needed.
-template MOJO_SYSTEM_EXPORT bool VerifyUserPointerForSize<1>(
+template MOJO_SYSTEM_IMPL_EXPORT bool VerifyUserPointerForSize<1>(
     const void*, size_t);
-template MOJO_SYSTEM_EXPORT bool VerifyUserPointerForSize<4>(
+template MOJO_SYSTEM_IMPL_EXPORT bool VerifyUserPointerForSize<4>(
     const void*, size_t);
 
 }  // namespace system