Compiling via make does not work -fix

[spaceKelan]

Hi there,

I had to do two things to make

1. I need to add a gcc flag in the Makefile
   
   Important! It must be the gnu99 flag not the c99 flag!
   In line 58:

CFLAGS += -std=gnu99

If you use latter, it will open the box of pandora, complaining about not finding code which actually exists in included headers

3. I need to comment something out in CO_error.h
   
   I must say I only found contradicting info regarding the error online, so as long as I don't use custom error definitions, I leave it like that.

// #if __has_include("CO_error_custom.h")
//     #include "CO_error_custom.h"
// #else
#include "CO_error_msgs.h"
// #endif

I don't know if this is due to me using CentOS7, but maybe this could be considered.

Thank you