[Ada] Enable use of GNAT.Sockets for VxWorks RTP

The recent introduction of GNAT.Sockets IPv6 support broke support for
VxWorks RTPs due to the use of internal VxWorks kernel calls. This patch
rectifies this by using the VxWorks public API for these routines.

The following RTP should compile successfully on a Development profile
VxWorks kernel that includes the INCLUDE_GETNAMEINFO component:

with GNAT.Sockets;      use GNAT.Sockets;

procedure IPvX is
   procedure Print_Address_Info
     (Host, Serv   : String;
      Family       : Family_Type := Family_Unspec)
   is
      Addresses : Address_Info_Array :=
        Get_Address_Info
          (Host, Serv, Family,
           Passive      => False,
           Numeric_Host => False);
   begin
      Sort (Addresses, IPv6_TCP_Preferred'Access);
   end Print_Address_Info;

begin
   Print_Address_Info ("localhost", "ssh");
end IPvX;

2019-08-19  Patrick Bernardi  <bernardi@adacore.com>

gcc/ada/

	* socket.c: Removed the redefinition of getaddrinfo, getnameinfo
	and freeaddrinfo to internal VxWorks kernel calls because they
	are, well, internal kernel calls and cannot be called from RTPs.
	VxWorks provides the necessary components to call these routines
	directly.

From-SVN: r274651

gcc/ada/ChangeLog

+2019-08-19  Patrick Bernardi  <bernardi@adacore.com>
+
+	* socket.c: Removed the redefinition of getaddrinfo, getnameinfo
+	and freeaddrinfo to internal VxWorks kernel calls because they
+	are, well, internal kernel calls and cannot be called from RTPs.
+	VxWorks provides the necessary components to call these routines
+	directly.
+
 2019-08-19  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* exp_dist.adb (Is_Generic_Actual_Subtype): New predicate.

gcc/ada/socket.c

@@ -704,12 +704,6 @@ __gnat_servent_s_proto (struct servent * s)
 
 #if defined(AF_INET6) && !defined(__rtems__)
 
-#if defined (__vxworks)
-#define getaddrinfo ipcom_getaddrinfo
-#define getnameinfo ipcom_getnameinfo
-#define freeaddrinfo ipcom_freeaddrinfo
-#endif
-
 int __gnat_getaddrinfo(
   const char *node,
   const char *service,