Added <errno.h> include to make compilation with CLang successfully

[StormBytePP]

Clang compiler seems not to autoadd some header files, in this case it fails because usage of errno is undefined.

Adding include for errno.h fixes the issue and makes compilation successful, also it might help for future gcc releases in case they decide to clean header includes.

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
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[StormBytePP]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.You have signed the CLA already but the status is still pending? Let us recheck it.

Unfortunatelly when I click on the link to sign the Contributor License it gives a blank "Version" field and no sign options