[Ada] GNAT.Sockets: fix recent regressions

[Ada] GNAT.Sockets: fix recent regressions

The support for IPv6 that was added since last release triggered
regressions on various platforms. The size of structures passed to low
level routines was not correct anymore: it should depend on the address
family, now.

2019-03-22  Dmitriy Anisimkov  <anisimko@adacore.com>

gcc/ada/

	PR ada/89583
	* libgnat/g-socket.adb (Bind_Socket, Connect_Socket,
	Send_Socket): Fix the computation of structure lengths passed to
	low level routines.
	(Is_IPv6_Address): Fix the number of expected colons.

2019-03-22  Simon Wright  <simon@pushface.org>

gcc/testsuite/

	PR ada/89583
	* gnat.dg/socket2.adb: New.

From-SVN: r269873