Really determine availability of all stdtoxx_l() functions

The case of missing strtod_l() is already handled by 9507bc430e
(Determine availability of the required xlocale API by compiling,
2017-04-14).

Similarly test for all the strto*_l() functions used by wx instead of
assuming that they are available if strtod_l() is.

It appears that the 'musl' C standard library, used on e.g. Alpine
Linux, does have strtod_l(), but not the others. Because of which this
check did not properly disable the feature, and compilation would fail.

Closes https://github.com/wxWidgets/wxWidgets/pull/2451

configure

@@ -35389,6 +35389,8 @@ main ()
 
         locale_t t;
         strtod_l(NULL, NULL, t);
+        strtol_l(NULL, NULL, 0, t);
+        strtoul_l(NULL, NULL, 0, t);
 
   ;
   return 0;

configure.in

@@ -6136,6 +6136,8 @@ if test "$wxUSE_XLOCALE" = "yes" ; then
         [
         locale_t t;
         strtod_l(NULL, NULL, t);
+        strtol_l(NULL, NULL, 0, t);
+        strtoul_l(NULL, NULL, 0, t);
         ],
         wx_cv_type_locale_t=yes,
         wx_cv_type_locale_t=no