Privatize useful.h and avl.h
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index 45cee35..173be45 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -203,6 +203,7 @@
'src/cpp/util/time_cc.cc',
'src/cpp/codegen/codegen_init.cc',
'src/core/lib/gpr/arena.h',
+ 'src/core/lib/gpr/avl.h',
'src/core/lib/gpr/env.h',
'src/core/lib/gpr/fork.h',
'src/core/lib/gpr/mpscq.h',
@@ -213,6 +214,7 @@
'src/core/lib/gpr/thd_internal.h',
'src/core/lib/gpr/time_precise.h',
'src/core/lib/gpr/tmpfile.h',
+ 'src/core/lib/gpr/useful.h',
'src/core/lib/gprpp/abstract.h',
'src/core/lib/gprpp/atomic.h',
'src/core/lib/gprpp/atomic_with_atm.h',
@@ -449,6 +451,7 @@
'src/cpp/server/thread_pool_interface.h',
'src/cpp/thread_manager/thread_manager.h',
'src/core/lib/gpr/arena.h',
+ 'src/core/lib/gpr/avl.h',
'src/core/lib/gpr/env.h',
'src/core/lib/gpr/fork.h',
'src/core/lib/gpr/mpscq.h',
@@ -459,6 +462,7 @@
'src/core/lib/gpr/thd_internal.h',
'src/core/lib/gpr/time_precise.h',
'src/core/lib/gpr/tmpfile.h',
+ 'src/core/lib/gpr/useful.h',
'src/core/lib/gprpp/abstract.h',
'src/core/lib/gprpp/atomic.h',
'src/core/lib/gprpp/atomic_with_atm.h',