Should not explicitly initialize these pointers to nullptr in gcc-4.4 case

because nullptr assignment actually requires the calling of a constructor.
As a result, the order in which these nullptr initializations take place
is not defined with respect to other initializations.
A pointer that is left without explicit initialization automatically
gets nullptr anyway, so just don't explicitly initialize these.

src/cpp/codegen/codegen_init.cc

@@ -34,12 +34,12 @@
 #include <grpc++/impl/codegen/core_codegen_interface.h>
 #include <grpc++/impl/codegen/grpc_library.h>
 
-/// Initializes the global gRPC variables for the codegen library. These will
+/// Null-initializes the global gRPC variables for the codegen library. These
 /// stay null in the absence of of grpc++ library. In this case, no gRPC
 /// features such as the ability to perform calls will be available. Trying to
 /// perform them would result in a segmentation fault when trying to deference
 /// the following nulled globals. These should be associated with actual
 /// as part of the instantiation of a \a grpc::GrpcLibraryInitializer variable.
 
-grpc::CoreCodegenInterface* grpc::g_core_codegen_interface = nullptr;
+grpc::CoreCodegenInterface* grpc::g_core_codegen_interface;
-grpc::GrpcLibraryInterface* grpc::g_glip = nullptr;
+grpc::GrpcLibraryInterface* grpc::g_glip;