storage class specifier is deprecated and incompatible with C++17

Found via Travis CI

Attributes GH PR #788: https://github.com/ArcticaProject/nx-libs/pull/788

Attributes ArcticaProject/nx-libs#382

  commit cc5f09c86f7bea23b7546c3491b2c52ce8100a71
  Author: Alan Coopersmith <alan.coopersmith@oracle.com>
  Date:   Mon Jul 9 19:12:43 2012 -0700

    Use C99 designated initializers in various extension Replies
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
Tested-by: Daniel Stone <daniel@fooishbar.org>

Attributes ArcticaProject/nx-libs#382

  commit cdf5bcd420e5bcf4a4a24a275d3133a4e16ce41e
  Author: Alan Coopersmith <alan.coopersmith@oracle.com>
  Date:   Mon Jul 9 19:12:42 2012 -0700

    Use calloc to zero fill buffers being allocated for replies & events

    Ensures padding bytes are zero-filled
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
Tested-by: Daniel Stone <daniel@fooishbar.org>

Attributes ArcticaProject/nx-libs#382

Fixes ArcticaProject/nx-libs#399

reflect the version of libX11 we are basing on

Attributes GH PR 778: https://github.com/ArcticaProject/nx-libs/pull/778

 Fixes ArcticaProject/nx-libs#768.

 This reverts commit 889de46f.

 Fixes ArcticaProject/nx-libs#775.

 Fixes ArcticaProject/nx-libs#777.

Attributes GH PR #776: https://github.com/ArcticaProject/nx-libs/pull/776

The old unix-* session types are deprecated and will always
lead to a warning message "Unrecognized session type".

Internally there are only three session types: agent, proxy
and shadow, all the others are mapped to one of those three.

Attributes GH PR #774: https://github.com/ArcticaProject/nx-libs/pull/774

These keystrokes where the same as their viewport_scroll variants and made
the latter being disabled.

Fixes ArcticaProject/nx-libs#770

Attributes GH PR #773: https://github.com/ArcticaProject/nx-libs/pull/773

Fixes ArcticaProject/nx-libs#772.

This reverts commit 16cd2bbe.

It turned out that I had missed some of the Booleans being actually
tristate variables. I think I can fix this (they do not need to be
tristate) but I revert this for now to get back to a working state
(there are reports about non-working fullscreen mode and reconnect
problems).

Refers to ArcticaProject/nx-libs#772

Attributes GH PR #766: https://github.com/ArcticaProject/nx-libs/pull/766

drop "== False", "== 0", "== True" and "== 0" for nxagentOptions and Traps

In rootless mode skip processing user geometry stuff since the values will we
overwritten later anyway.

Fixes: ArcticaProject/nx-libs#765

Attributes GH PR #764: https://github.com/ArcticaProject/nx-libs/pull/764

This fixes the verification in validateSpec()

Attributes GH PR #761: https://github.com/ArcticaProject/nx-libs/pull/761

If nxagent is started in fullscreen mode take care the saved size
(that is applied on exit of the fullscreen mode) will be configured
correctly. Also respect a user provided -geometry option (had been
ignored here previously).

Fixes ArcticaProject/nx-libs#449

There's no need to reduce the size to 75% in rootless mode. We always
want to have the full size then.

Fixes ArcticaProject/nx-libs#757 (Part 2/2)

... by using some short named variables and the min() macro.

No change in behaviour.