[AD] Patch to tidy up the _al_strdup() function (4.3.10)

[Colin Ward <lists@xxxxxxxxxx>]

A while ago I submitted a patch for _al_strdup() similar to today's
_al_ustrdup() patch.  However, in the implemenetation of the function I
added a parameter that was const char instead of AL_CONST char, which is
inconsistent.  I was learning.  :-)

The attached tiny patch fixes that.

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--- src/allegro.c	(revision 11109)
+++ src/allegro.c	(working copy)
@@ -716,7 +716,7 @@
  *  uses any user overloaded memory allocation system in use.
  *  The result of this function _must_ be freed with _AL_FREE().
  */
-char *_al_strdup(const char *string)
+char *_al_strdup(AL_CONST char *string)
 {
    char *newstring = _AL_MALLOC(strlen(string) + 1);