Microchip XC32 no longer supports sys/errno.h from V4.0

[mrberman87]

Pre-processor compiler version flags for this change come from ( https://github.com/Microchip-MPLAB-Harmony/net/blob/2dd23ebaccec29104b8c9ab5614dbb0112f2bf8c/tcpip/src/berkeley_api.c#L53 ).

[wolfSSL-Bot]

Can one of the wolfSSL admins verify this patch?

[embhorn]

Hello @mrberman87

Thanks for this code change. We do not typically accept small code revisions, but I was able to incorporate the change into the next release.

Thanks, @embhorn - wolfSSL Support

[embhorn]

Closing in favor of #316