make: fix GCC warnings

@@ -67,14 +67,16 @@
 
 /*
  * Static variables
  */
 #ifdef SUN5_0
-extern "C" void         (*sigivalue)(int) = SIG_DFL;
-extern "C" void         (*sigqvalue)(int) = SIG_DFL;
-extern "C" void         (*sigtvalue)(int) = SIG_DFL;
-extern "C" void         (*sighvalue)(int) = SIG_DFL;
+extern "C" {
+        void            (*sigivalue)(int) = SIG_DFL;
+        void            (*sigqvalue)(int) = SIG_DFL;
+        void            (*sigtvalue)(int) = SIG_DFL;
+        void            (*sighvalue)(int) = SIG_DFL;
+}
 #else
 static  void            (*sigivalue)(int) = (void (*) (int)) SIG_DFL;
 static  void            (*sigqvalue)(int) = (void (*) (int)) SIG_DFL;
 static  void            (*sigtvalue)(int) = (void (*) (int)) SIG_DFL;
 static  void            (*sighvalue)(int) = (void (*) (int)) SIG_DFL;

@@ -323,11 +325,11 @@
  *              char_semantics  The vector of character semantics that we set
  */
 void
 setup_char_semantics(void)
 {
-        char            *s;
+        const char      *s;
         wchar_t         wc_buffer[1];
         int             entry;
 
         if (svr4) {
                 s = "@-";

@@ -411,11 +413,11 @@
  *              format          printf type format string
  *              args            Arguments to match the format
  */
 /*VARARGS*/
 void
-fatal_mksh(char * message, ...)
+fatal_mksh(const char *message, ...)
 {
         va_list args;
         char    *buf = static_buf;
         char    *mksh_fat_err = catgets(libmksdmsi18n_catd, 1, 128, "mksh: Fatal error: ");
         char    *cur_wrk_dir = catgets(libmksdmsi18n_catd, 1, 129, "Current working directory: ");

@@ -466,11 +468,11 @@
  *              format          printf style format string
  *              args            arguments to match the format
  */
 /*VARARGS*/
 void
-fatal_reader_mksh(char * pattern, ...)
+fatal_reader_mksh(const char * pattern, ...)
 {
         va_list args;
         char    message[1000];
 
         va_start(args, pattern);