Patch out MECC DER

* replaces -b dummy option in dbclient to be similar with openssh -b option
* useful in multi-wan connections

Server chosen tcpfwd ports

configure: add a variable to allow openpty check to be cached

Some linting, const parameters

Argument no. 3 nominally inconsistent with format (int vs. unsigned int)

Signed-off-by: Dengke Du <dengke.du@windriver.com>

From William K. Foster.

dropbear server: support -T max auth tries

sysoptions.h: Add ability to override DROPBEAR_LISTEN_BACKLOG

Add support for '-T n' for a run-time specification for maximum number
of authentication attempts where 'n' is between 1 and compile time
option MAX_AUTH_TRIES.

A default number of tries can be specified at compile time using
'DEFAULT_AUTH_TRIES' which itself defaults to MAX_AUTH_TRIES for
backwards compatibility.

Signed-off-by: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>

print key size with dropbearkey