Only declare the origpriority variable if we support priority.

This fixes the following compiler warning when building for Windows:

net_packet.c: In function ‘send_udppacket’:
net_packet.c:633:6: error: unused variable ‘origpriority’ [-Werror=unused-variable]
  int origpriority = origpkt->priority;
        ^
Remove an unnecessary pointer dereference in execute_script().

This fixes the following compiler warning when building for Windows:

script.c: In function ‘execute_script’:
script.c:52:5: error: value computed is not used [-Werror=unused-value]
     *q++;
          ^
Fix callback signature for TAP-Win32 device_handle_read().

This fixes the following compiler warning when building for Windows:

mingw/device.c: In function ‘setup_device’:
mingw/device.c:186:2: error: passing argument 2 of ‘io_add_event’ from incompatible pointer type [-Werror]
  io_add_event(&device_read_io, device_handle_read, NULL, CreateEvent(NULL, TRUE, FALSE, NULL));
  ^
In file included from mingw/../net.h:27:0,
                 from mingw/../subnet.h:24,
                 from mingw/../conf.h:34,
                 from mingw/device.c:26:
mingw/../event.h:61:13: note: expected ‘io_cb_t’ but argument is of type ‘void (*)(void *)’
 extern void io_add_event(io_t *io, io_cb_t cb, void* data, WSAEVENT event);
Remove unused variable in TAP-Win32 setup_device().

This fixes the following compiler warning when building for Windows:

mingw/device.c: In function ‘setup_device’:
mingw/device.c:92:9: error: unused variable ‘thread’ [-Werror=unused-variable]
  HANDLE thread;
           ^
Remove unused device stats variables.

This removes a bunch of variables that are never actually used anywhere.

This fixes the following compiler warning when building for Windows:

mingw/device.c:46:17: error: ‘device_total_in’ defined but not used [-Werror=unused-variable]
 static uint64_t device_total_in = 0;
                  ^
Resolve KEY_EVENT conflict between Windows and ncurses.

This fixes the following compiler warning when building for Windows:

In file included from top.c:24:0:
/usr/local/mingw/ncurses/include/curses.h:1478:0: error: "KEY_EVENT" redefined [-Werror]
 #define KEY_EVENT 0633  /* We were interrupted by an event */
 ^
In file included from /usr/share/mingw-w64/include/windows.h:74:0,
                 from /usr/share/mingw-w64/include/winsock2.h:23,
                 from have.h:46,
                 from system.h:26,
                 from top.c:20:
/usr/share/mingw-w64/include/wincon.h:101:0: note: this is the location of the previous definition
 #define KEY_EVENT 0x1
 ^
Check if devops is valid before closing the device.

This fixes a segfault that occurs on exit if tinc fails before the
device is initialized (for example, if it fails to read the private
key).
Shutdown cleanly when receiving a Windows console shutdown request.

This commit makes tinc exit cleanly on Windows when hitting CTRL+C at
the console or when the user logs off. This change has no effect when
running tinc as a service.
Fix "tinc start" on Windows when the path contains spaces.

When invoking "tinc start" with spaces in the path, the following
happens:

    > "c:\Program Files (x86)\tinc\tinc.exe" start
    c:\Program: unrecognized argument 'Files'
    Try `c:\Program --help' for more information.

This is caused by inconsistent handling of command line strings between
execvp() and the spawned process' CRT, as documented on MSDN:
http://msdn.microsoft.com/library/431x4c1w.aspx
Improve subprocess behavior in tinc start command.

When invoking tincd, tinc start currently uses the execvp() function,
which doesn't behave well in a console as the console displays a new
prompt before the subprocess finishes (which makes me suspect the exit
value is not handled at all). This new code uses spawnvp() instead,
which seems like a better fit.
Add documentation about using system-assigned ports.

There are two caveats to be aware of which are documented in this
commit:

 - Because the system will likely assign different ports when binding
   several times to different address families, it is recommended to
   only use a single address family, otherwise other nodes will only
   get one port among the several that were assigned, possibly breaking
   communication.

 - AutoConnect won't work in this scenario, because it relies on the UDP
   port being the same as the TCP port, which is not the case when using
   system-assigned ports.
Verify seqno early in sptps_verify_datagram().

This is a slight optimization for sptps_verify_datagram(), which might
come in handy since this function is called in a loop via try_harder().

It turns out that since sptps_verify_datagram() doesn't update any
state, it doesn't matter in which order verifications are done. However,
it does affect performance since it's much cheaper to check the seqno
than to try to decrypt the packet.

Since this function is called with the wrong node most of the time, it
makes verification vastly faster for the majority of calls because the
seqno will be wrong in most cases.
Merge branch 'winwarnings' of https://github.com/dechamps/tinc into 1.1
Merge branch 'ctrl' of https://github.com/dechamps/tinc into 1.1
Merge branch 'tincstart' of https://github.com/dechamps/tinc into 1.1
Merge branch 'keysegfault' of https://github.com/dechamps/tinc into 1.1