hello-2.1.91 modernization

[Bruno Haible]

Since the purpose of is to show best practices, here are a few of them.
- The double-inclusion guard in system.h is incomplete.
- A comment refers to <getopt.h> and <unistd.h> as being "ANSI C89 headers",
  which is wrong. These are POSIX.
- Declaration of variables as 'const' where possible. Improves the legibility
  of the program.
- Declaration of variables and functions as 'static' where possible. Necessary
  discipline for large programs.
- #if HAVE_... instead of #ifdef HAVE_...


2006-08-21  Bruno Haible  <address@hidden>

        * src/system.h: Fix double-inclusion guard. Improve comments.
        * src/hello.c (longopts): Make const and static.
        (main): Convert to ANSI C definition.

*** src/system.h.bak    Sun Jul 16 17:57:46 2006
--- src/system.h        Tue Aug 22 01:27:04 2006
***************
*** 16,28 ****
     Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  
  #ifndef HELLO_SYSTEM_H
  
  /* Assume ANSI C89 headers are available.  */
- #include <getopt.h>
  #include <locale.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  
  /* Internationalization.  */
--- 16,32 ----
     Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  
  #ifndef HELLO_SYSTEM_H
+ #define HELLO_SYSTEM_H
  
  /* Assume ANSI C89 headers are available.  */
  #include <locale.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
+ 
+ /* Use POSIX headers.  If they are not available, we use the substitute
+    provided by gnulib.  */
+ #include <getopt.h>
  #include <unistd.h>
  
  /* Internationalization.  */
*** src/hello.c.bak     Tue Aug 22 01:17:09 2006
--- src/hello.c Tue Aug 22 01:20:41 2006
***************
*** 23,29 ****
  /* String containing name the program is called with.  */
  const char *program_name;
  
! struct option longopts[] =
  {
    { "greeting", required_argument, NULL, 'g' },
    { "help", no_argument, NULL, 'h' },
--- 23,29 ----
  /* String containing name the program is called with.  */
  const char *program_name;
  
! static const struct option longopts[] =
  {
    { "greeting", required_argument, NULL, 'g' },
    { "help", no_argument, NULL, 'h' },
***************
*** 34,42 ****
  };
  
  int
! main (argc, argv)
!      int argc;
!      char *argv[];
  {
    int optc;
    int h = 0, v = 0, t = 0, n = 0, lose = 0;
--- 34,40 ----
  };
  
  int
! main (int argc, char *argv[])
  {
    int optc;
    int h = 0, v = 0, t = 0, n = 0, lose = 0;
***************
*** 44,50 ****
  
    program_name = argv[0];
  
! #ifdef HAVE_SETLOCALE
    /* Set locale via LC_ALL.  */
    setlocale (LC_ALL, "");
  #endif
--- 42,48 ----
  
    program_name = argv[0];
  
! #if HAVE_SETLOCALE
    /* Set locale via LC_ALL.  */
    setlocale (LC_ALL, "");
  #endif