export and unset builtins

[jdagz28]

Resolved merge conflicts on the following files. builtins.c

• Deleted comment if (ft_strncmp_twice((const char*)command.argv[0], "./minishell"))
• It is ran as command, similar to script files.
• Delete if exit --- retained working implementation

Check_opred.c

• Retained updated syntax checks

Shell_run function in shell.c

• Retained master implementation – as void
• use of get_exit_value
• Removed printf(‘exit\n’);