Adding error messages for debug purposes

[Icaro-Lima]

My intention with this patch is to map error codes to friendlier error messages, just as they are in the current sgx documentation ( e.g. here) It is worth remembering that the error message will depend on the function that throws the error and the error code.

Currently, for most samples (here), you have put a list of errors in each app.cpp, taking much of the code and complicating it unnecessarily.

Some examples where something similar has been implemented:

• OpenSSL here
• Libgcrypt here
• Linux here
• OpenGL here
• Cuda here
• dlib here
• boost here
  ...

[Icaro-Lima]

I'm wondering if I should change the word "error" to "status". On the other hand, "SGX_SUCCESS" is in the file "sgx_error.h", even indicating success.

[andyzyb]

This patch is unlikely to be accepted since it is not clearly stating which problem to solve. If it is just to convert an error code to a string, then it doesn't seem provide much value.

[Icaro-Lima]

I disagree, debug messages are one of the major reason for extensive code at least in the ones I write and in the sample codes from this repository. I'll edit the merge request message to make it clearer.

[pdxjohnny]

I also think that this is useful. I did something similar and then went and looked at PRs and saw this. I think its important to have some function like this or the one I added (which is admittedly very basic). But some way of quickly doing an error code -> string of the message or string of the description. Preferably both