tcpip-forward.c: Removed unused variables shost, sport and sockopt
misc.c: Fixed warning about unused parameter abstract
wincng.h: Fixed warning about pointer targets differing in signedness
libgcrypt.h: Fixed warning about pointer targets differing in signedness
misc.c: Fixed warning about mixed declarations and code
tcpip-forward.c: Fixed warning that pointer targets differ in signedness

libssh2_channel_forward_listen_ex uses ints instead of unsigned ints.
wincng.c: Fixed warning about pointer targets differing in signedness
knownhost.c: Fixed warning that pointer targets differ in signedness
libssh2_priv.h: a 1 bit bit-field should be unsigned

some compilers may not like this
configure: Display individual crypto backends on separate lines

This avoids line-wrapping in between parameters and makes the
error message look like the following:

configure: error: No crypto library found!
Try --with-libssl-prefix=PATH
 or --with-libgcrypt-prefix=PATH
 or --with-wincng on Windows