Fix compile errors, code review feedback, and add basic libc test suite.

*** 112,123 ****
          .messages = &lc_messages_posix,
          .time = &lc_time_posix,
          .runelocale = &_DefaultRuneLocale,
  };
  
! locale_t __global_locale = &posix_locale;
  
  /*
   * Category names for getenv()  Note that this was modified
   * for Solaris.  See <iso/locale_iso.h>.
   */
  #define NUM_CATS        7
--- 112,129 ----
          .messages = &lc_messages_posix,
          .time = &lc_time_posix,
          .runelocale = &_DefaultRuneLocale,
  };
  
! locale_t ___global_locale = &posix_locale;
  
+ locale_t
+ __global_locale(void)
+ {
+         return (___global_locale);
+ }
+ 
  /*
   * Category names for getenv()  Note that this was modified
   * for Solaris.  See <iso/locale_iso.h>.
   */
  #define NUM_CATS        7
*** 394,404 ****
  
          if (catmask & ~(LC_ALL_MASK)) {
                  errno = EINVAL;
                  return (NULL);
          }
!         loc = duplocale(base != NULL ? base : __global_locale);
          if (loc == NULL) {
                  return (NULL);
          }
  
          for (i = 0; i < LC_ALL; i++) {
--- 400,410 ----
  
          if (catmask & ~(LC_ALL_MASK)) {
                  errno = EINVAL;
                  return (NULL);
          }
!         loc = duplocale(base != NULL ? base : ___global_locale);
          if (loc == NULL) {
                  return (NULL);
          }
  
          for (i = 0; i < LC_ALL; i++) {
*** 416,426 ****
                          return (NULL);
                  }
                  __locdata_release(loc->locdata[i]);
                  loc->locdata[i] = ldata;
          }
!         if (base && base != __global_locale) {
                  freelocale(base);
          }
          loc->collate = loc->locdata[LC_COLLATE]->l_data[0];
          loc->ctype = loc->locdata[LC_CTYPE]->l_data[0];
          loc->runelocale = loc->locdata[LC_CTYPE]->l_data[1];
--- 422,432 ----
                          return (NULL);
                  }
                  __locdata_release(loc->locdata[i]);
                  loc->locdata[i] = ldata;
          }
!         if (base && base != ___global_locale) {
                  freelocale(base);
          }
          loc->collate = loc->locdata[LC_COLLATE]->l_data[0];
          loc->ctype = loc->locdata[LC_CTYPE]->l_data[0];
          loc->runelocale = loc->locdata[LC_CTYPE]->l_data[1];
*** 432,442 ****
  }
  
  locale_t
  uselocale(locale_t loc)
  {
!         locale_t lastloc = __global_locale;
          locale_t *locptr;
  
          locptr = tsdalloc(_T_SETLOCALE, sizeof (locale_t), freelocptr);
          /* Should never occur */
          if (locptr == NULL) {
--- 438,448 ----
  }
  
  locale_t
  uselocale(locale_t loc)
  {
!         locale_t lastloc = ___global_locale;
          locale_t *locptr;
  
          locptr = tsdalloc(_T_SETLOCALE, sizeof (locale_t), freelocptr);
          /* Should never occur */
          if (locptr == NULL) {
*** 451,461 ****
          if (loc != NULL) {
                  /*
                   * Set it to LC_GLOBAL_LOCAL to return to using
                   * the global locale (setlocale).
                   */
!                 if (loc == __global_locale) {
                          *locptr = NULL;
                  } else {
                          /* No validation of the provided locale at present */
                          *locptr = loc;
                  }
--- 457,467 ----
          if (loc != NULL) {
                  /*
                   * Set it to LC_GLOBAL_LOCAL to return to using
                   * the global locale (setlocale).
                   */
!                 if (loc == ___global_locale) {
                          *locptr = NULL;
                  } else {
                          /* No validation of the provided locale at present */
                          *locptr = loc;
                  }