Add -no_alt_chains option to apps to implement the new

X509_V_FLAG_NO_ALT_CHAINS flag. Using this option means that when building
certificate chains, the first chain found will be the one used. Without this
flag, if the first chain found is not trusted then we will keep looking to
see if we can build an alternative chain instead.

Reviewed-by: Dr. Stephen Henson <steve@openssl.org>