[hackers] [quark] Import fixed arg.h from farbfeld || Laslo Hunhold

[git]

commit 84d77d096b79b201e43e87efe7ad4f9dadc3dfa6
Author:     Laslo Hunhold <d...@frign.de>
AuthorDate: Wed Aug 2 13:54:10 2017 +0200
Commit:     Laslo Hunhold <d...@frign.de>
CommitDate: Wed Aug 2 13:54:10 2017 +0200

    Import fixed arg.h from farbfeld
    
    This fixes the handling of a { NULL } argv[] without returning argc =
    -1.

diff --git a/arg.h b/arg.h
index 003f8ec..cf30d65 100644
--- a/arg.h
+++ b/arg.h
@@ -22,7 +22,7 @@
 extern char *argv0;
 
 /* int main(int argc, char *argv[]) */
-#define ARGBEGIN for (argv0 = *argv, argc--, argv++;                           
   \
+#define ARGBEGIN for (argv0 = *argv, *argv ? (argc--, argv++) : ((void *)0);   
   \
                       *argv && (*argv)[0] == '-' && (*argv)[1]; argc--, 
argv++) { \
                        int argparsed;                                          
  \
                        if ((*argv)[1] == '-' && (*argv)[2] == '\0') {          
  \