SSL: fixed ssl_buffer_size on SNI virtual hosts (ticket #1192). Previously, buffer size was not changed from the one saved during initial ngx_ssl_create_connection(), even if the buffer itself was not yet created. Fix is to change c->ssl->buffer_size in the SNI callback. Note that it should be also possible to update buffer size even in non-SNI virtual hosts as long as the buffer is not yet allocated. This looks like an overcomplication though.