Make thread_pool.h a public header
Rename ThreadPool -> FixedSizeThreadPool to allow for later introduction
of DynamicSizeThreadPool
diff --git a/tools/doxygen/Doxyfile.c++ b/tools/doxygen/Doxyfile.c++
index feb7ad8..e82e3bc 100644
--- a/tools/doxygen/Doxyfile.c++
+++ b/tools/doxygen/Doxyfile.c++
@@ -796,6 +796,7 @@
 include/grpc++/status.h \
 include/grpc++/status_code_enum.h \
 include/grpc++/stream.h \
+include/grpc++/thread_pool.h \
 include/grpc++/thread_pool_interface.h \
 include/grpc++/time.h