gio: actually install and reference gnativesocketaddress.h.

The header file was installed when building using autotools, but was
inadvertently omitted in the meson targets.

Luckily, ABI is not impacted, since gnativesocketaddress.c was always
compiled and linked into libgio.

Fixes: #1854

gio/gio.h

@@ -93,6 +93,7 @@
 #include <gio/gmemoryoutputstream.h>
 #include <gio/gmount.h>
 #include <gio/gmountoperation.h>
+#include <gio/gnativesocketaddress.h>
 #include <gio/gnativevolumemonitor.h>
 #include <gio/gnetworkaddress.h>
 #include <gio/gnetworkmonitor.h>

gio/meson.build

@@ -672,6 +672,7 @@ gio_headers = files(
   'gmemoryinputstream.h',
   'gmemoryoutputstream.h',
   'gmountoperation.h',
+  'gnativesocketaddress.h',
   'gnativevolumemonitor.h',
   'gnetworkaddress.h',
   'gnetworkmonitor.h',