Add xstrtokenize to the dix.

Move tokenize out of the parser, make it a dix util function instead.
Splitting a string into multiple substrings is useful by other places, so
let's use it across the line. Future users include config/hal, config/udev
and of course the parser.

Example usage:
char **substrings = xstrtokenize(my_string, "\n");

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Dan Nicholson <dbn.lists@gmail.com>

os/utils.c

@@ -1870,6 +1870,46 @@ CheckUserAuthorization(void)
 #endif
 }
 
+/*
+ * Tokenize a string into a NULL terminated array of strings. Always returns
+ * an allocated array unless an error occurs.
+ */
+char**
+xstrtokenize(const char *str, const char *separators)
+{
+    char **list, **nlist;
+    char *tok, *tmp;
+    unsigned num = 0, n;
+
+    if (!str)
+        return NULL;
+    list = calloc(1, sizeof(*list));
+    if (!list)
+        return NULL;
+    tmp = strdup(str);
+    if (!tmp)
+        goto error;
+    for (tok = strtok(tmp, separators); tok; tok = strtok(NULL, separators)) {
+        nlist = realloc(list, (num + 2) * sizeof(*list));
+        if (!nlist)
+            goto error;
+        list = nlist;
+        list[num] = strdup(tok);
+        if (!list[num])
+            goto error;
+        list[++num] = NULL;
+    }
+    free(tmp);
+    return list;
+
+error:
+    free(tmp);
+    for (n = 0; n < num; n++)
+        free(list[n]);
+    free(list);
+    return NULL;
+}
+
 #ifdef __SCO__
 #include <fcntl.h>