Allow running tinc without RSA keys.

This allows one to run tinc with only Ed25519 keys, forcing tinc to
always use the SPTPS protocol.
Update THANKS file.
Check whether res_init() really lives in libresolv.

On some platforms (Mac OS X for example), the res_init() function requires
linking with libresolv. On others (Linux, OpenBSD for example), res_init()
lives in libc.
BSD make doesn't like .PHONY .c files.

It then thinks there should be a rule to make the .c file, which does
not exist of course. Luckily, we can tell it that version.o is .PHONY,
and this will still cause the .o file to be regenerated and linked into
the binaries everytime make is called.
We don't depend on ECDH functions from OpenSSL anymore.
Linux doesn't like .PHONY .o files.

In order to please every OS, make version.c .PHONY again, and add an
empty rule to make version.c.
Remove AES-GCM support.
Better default paths for log and PID files on Windows.
Add BroadcastSubnet and DeviceStandby options to the manual and completion.
Releasing 1.1pre11.