Inconsistent int signedness for printf

The Protocol's Type Message ENUM is inconsistent with "printf" for c_glib and might be in some cases for C++.
The issue can be seen at compiling with the flag " -Wformat-signedness".

Looks like all the printf use "%d" signed-i32 - in order to keep it consistent. It be better to have enum of type int32_t or unsigned with printf to be changed to "%u" - or further more reduce it to uint8_t (unless Message Type needs to be reserved for growing in future)

The printf cases can be found at https://github.com/apache/thrift/search?q="invalid+message+type+%25d%2C"&type=code

The corresponding ENUMs are the:

C++:
https://github.com/apache/thrift/blob/66d897667c451ef6560d89b979b7001c57a3eda6/lib/cpp/src/thrift/protocol/TEnum.h#L57

enum TMessageType {
  T_CALL       = 1,
  T_REPLY      = 2,
  T_EXCEPTION  = 3,
  T_ONEWAY     = 4
};

c_glib: 
https://github.com/apache/thrift/blob/66d897667c451ef6560d89b979b7001c57a3eda6/lib/c_glib/src/thrift/c_glib/protocol/thrift_protocol.h#L63

typedef enum {
  T_CALL      = 1,
  T_REPLY     = 2,
  T_EXCEPTION = 3,
  T_ONEWAY    = 4
} ThriftMessageType;

I'm willing to make a pull-request, Just I would like first to know if there are any preferences/considerations on the subject.