[Ovmsdev] Update WolfSSH/SSL

[Stephen Casner]

On Sun, 24 Jan 2021, Michael Balzer wrote:
> The higher base memory footprint due to the higher NetMan stack size + some
> additional buffer it seems (some 512 bytes?) means this needs to be checked
> with complex vehicle modules in live operation before merging, but I think
> that won't be an issue.

As suggested to me by WolfSSL support, there is a configuration
parameter for wolfssl to use heap allocation rather than stack for
some buffers and structures.  With that change, I can restore the
NetMan stack to 8K.  Now the comparison of memory usage is as follows:

  - With the current master code the max NetMan stack depth on my OVMS
    was 5616 whereas after the update it is 5760.

  - With the current master code, the amount of memory added by NetMan
    when an ssh connection was established was 2557 D/IRAM and 6108
    SPIRAM for 8665 total.  With the update it was 1056 D/IRAM and
    7532 SPIRAM for 8588 total.

I think this change should clear the way for merging into master.

                                                         -- Steve