Thread safety fixes.

*** 41,50 ****
--- 41,51 ----
  #include <locale.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  #include <stdio.h>
+ #include "mtlib.h"
  #include "collate.h"
  #include "lnumeric.h"   /* for struct lc_numeric */
  #include "lctype.h"     /* for struct lc_ctype */
  #include "setlocale.h"
  #include "../i18n/_loc_path.h"
*** 57,71 ****
  char    *_PathLocale = _DFLT_LOC_PATH;
  
  static char     *current_locale(locale_t, int);
  static void     install_legacy(locale_t, int);
  
  char *
  setlocale(int category, const char *locname)
  {
!         locale_t oldloc;
!         locale_t newloc;
          int mask;
  
          if (category < 0 || category > LC_ALL) {
                  errno = EINVAL;
                  return (NULL);
--- 58,75 ----
  char    *_PathLocale = _DFLT_LOC_PATH;
  
  static char     *current_locale(locale_t, int);
  static void     install_legacy(locale_t, int);
  
+ static mutex_t setlocale_lock = DEFAULTMUTEX;
+ static locale_t setlocale_list = NULL;
+ 
  char *
  setlocale(int category, const char *locname)
  {
!         locale_t loc;
!         locale_t srch;
          int mask;
  
          if (category < 0 || category > LC_ALL) {
                  errno = EINVAL;
                  return (NULL);
*** 72,99 ****
          }
  
          if (locname == NULL)
                  return (current_locale(___global_locale, category));
  
-         if ((oldloc = duplocale(___global_locale)) == NULL)
-                 return (NULL);
- 
          mask = (category == LC_ALL ? LC_ALL_MASK : (1 << category));
  
!         newloc = newlocale(mask, locname, oldloc);
!         if (newloc == NULL) {
!                 freelocale(oldloc);
                  return (NULL);
          }
  
!         oldloc = ___global_locale;
!         ___global_locale = newloc;
  
!         install_legacy(newloc, mask);
  
!         freelocale(oldloc);
!         return (current_locale(newloc, category));
  }
  
  static char *
  current_locale(locale_t loc, int cat)
  {
--- 76,125 ----
          }
  
          if (locname == NULL)
                  return (current_locale(___global_locale, category));
  
          mask = (category == LC_ALL ? LC_ALL_MASK : (1 << category));
  
!         loc = newlocale(mask, locname, NULL);
!         if (loc == NULL) {
                  return (NULL);
          }
  
!         /*
!          * This next logic looks to see if we have ever used the same locale
!          * settings before.  If so, we reuse it.  We avoid ever calling
!          * freelocale() on a locale setting built up by setlocale, this
!          * ensures that consumers (uselocale) will always be thread safe;
!          * the actual locale data objects are never freed, and unique
!          * locale objects are also never freed.  We reuse to avoid leaking
!          * memory in applications that call setlocale repeatedly.
!          */
!         lmutex_lock(&setlocale_lock);
!         for (srch = setlocale_list; srch != NULL; srch = srch->next) {
!                 if (memcmp(srch->locdata, loc->locdata,
!                     sizeof (loc->locdata[0]) * LC_ALL) != 0) {
!                         continue;
!                 }
!                 break;
!         }
  
!         if (srch == NULL) {
!                 /* this is a new locale, save it for reuse later */
!                 loc->next = setlocale_list;
!                 setlocale_list = loc;
!         } else {
!                 /* we already had it, toss the new, and use what we found */
!                 freelocale(loc);
!                 loc = srch;
!         }
!         ___global_locale = loc;
  
!         install_legacy(loc, mask);
!         lmutex_unlock(&setlocale_lock);
! 
!         return (current_locale(loc, category));
  }
  
  static char *
  current_locale(locale_t loc, int cat)
  {