Make configure probe for mbstowcs_l as well as wcstombs_l.

We previously supposed that any given platform would supply both or neither
of these functions, so that one configure test would be sufficient.  It now
appears that at least on AIX this is not the case ... which is likely an
AIX bug, but nonetheless we need to cope with it.  So use separate tests.
Per bug #6758; thanks to Andrew Hastie for doing the followup testing
needed to confirm what was happening.

Backpatch to 9.1, where we began using these functions.

src/backend/utils/adt/pg_locale.c

@@ -1205,17 +1205,17 @@ char2wchar(wchar_t *to, size_t tolen, const char *from, size_t fromlen,
 		else
 		{
 #ifdef HAVE_LOCALE_T
-#ifdef HAVE_WCSTOMBS_L
+#ifdef HAVE_MBSTOWCS_L
 			/* Use mbstowcs_l for nondefault locales */
 			result = mbstowcs_l(to, str, tolen, locale);
-#else							/* !HAVE_WCSTOMBS_L */
+#else							/* !HAVE_MBSTOWCS_L */
 			/* We have to temporarily set the locale as current ... ugh */
 			locale_t	save_locale = uselocale(locale);
 
 			result = mbstowcs(to, str, tolen);
 
 			uselocale(save_locale);
-#endif   /* HAVE_WCSTOMBS_L */
+#endif   /* HAVE_MBSTOWCS_L */
 #else							/* !HAVE_LOCALE_T */
 			/* Can't have locale != 0 without HAVE_LOCALE_T */
 			elog(ERROR, "mbstowcs_l is not available");

src/include/pg_config.h.in

@@ -333,6 +333,9 @@
 /* Define to 1 if `long long int' works and is 64 bits. */
 #undef HAVE_LONG_LONG_INT_64
 
+/* Define to 1 if you have the `mbstowcs_l' function. */
+#undef HAVE_MBSTOWCS_L
+
 /* Define to 1 if you have the `memmove' function. */
 #undef HAVE_MEMMOVE
 

src/include/pg_config.h.win32

@@ -249,6 +249,9 @@
 #define HAVE_LONG_LONG_INT_64
 #endif
 
+/* Define to 1 if you have the `mbstowcs_l' function. */
+#define HAVE_MBSTOWCS_L 1
+
 /* Define to 1 if you have the `memmove' function. */
 #define HAVE_MEMMOVE 1