Don't check for non-standatd xlocale.h in configure

Testing for xlocale.h was due to a misunderstanding, this header wasn't
supposed to define locale_t which is defined by locale.h itself and was
just some internal glibc header which was removed in its 2.26 release,
see

https://sourceware.org/glibc/wiki/Release/2.26#Removal_of_.27xlocale.h.27

Stop checking for it in configure and also don't always define
wxUSE_XLOCALE but only do it if the configure test succeeded.

configure

@@ -32907,12 +32907,9 @@ $as_echo "$as_me: WARNING: I18n code requires wxFile... disabled" >&2;}
 fi
 
 if test "$wxUSE_XLOCALE" = "yes" ; then
-    $as_echo "#define wxUSE_XLOCALE 1" >>confdefs.h
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for locale_t" >&5
-
+$as_echo_n "checking for locale_t... " >&6; }
-
+if ${wx_cv_type_locale_t+:} false; then :
-            { $as_echo "$as_me:${as_lineno-$LINENO}: checking for complete xlocale" >&5
-$as_echo_n "checking for complete xlocale... " >&6; }
-if ${wx_cv_func_strtod_l+:} false; then :
   $as_echo_n "(cached) " >&6
 else
 
@@ -32925,7 +32922,6 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
         cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-        #include <xlocale.h>
         #include <locale.h>
         #include <stdlib.h>
 
@@ -32941,9 +32937,9 @@ main ()
 }
 _ACEOF
 if ac_fn_cxx_try_compile "$LINENO"; then :
-  wx_cv_func_strtod_l=yes
+  wx_cv_type_locale_t=yes
 else
-  wx_cv_func_strtod_l=no
+  wx_cv_type_locale_t=no
 
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
@@ -32955,12 +32951,18 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $wx_cv_func_strtod_l" >&5
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $wx_cv_type_locale_t" >&5
-$as_echo "$wx_cv_func_strtod_l" >&6; }
+$as_echo "$wx_cv_type_locale_t" >&6; }
+
+    if test "$wx_cv_type_locale_t" = "yes" ; then
+        $as_echo "#define wxUSE_XLOCALE 1" >>confdefs.h
+
 
-    if test "$wx_cv_func_strtod_l" = "yes" ; then
                         $as_echo "#define HAVE_LOCALE_T 1" >>confdefs.h
 
+    else
+        { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: No locale_t support, wxXLocale won't be available" >&5
+$as_echo "$as_me: WARNING: No locale_t support, wxXLocale won't be available" >&2;}
     fi
 fi
 

configure.in

@@ -5757,17 +5757,11 @@ if test "$wxUSE_INTL" = "yes" ; then
 fi
 
 if test "$wxUSE_XLOCALE" = "yes" ; then
-    AC_DEFINE(wxUSE_XLOCALE)
+    AC_CACHE_CHECK([for locale_t], wx_cv_type_locale_t,
-
-    dnl even if xlocale.h exists, it may not contain all that
-    dnl wx needs. check if strtod_l() really is available.
-    AC_CACHE_CHECK([for complete xlocale],
-                   wx_cv_func_strtod_l,
     [
         AC_LANG_PUSH(C++)
         AC_TRY_COMPILE(
         [
-        #include <xlocale.h>
         #include <locale.h>
         #include <stdlib.h>
         ],
@@ -5775,16 +5769,20 @@ if test "$wxUSE_XLOCALE" = "yes" ; then
         locale_t t;
         strtod_l(NULL, NULL, t);
         ],
-        wx_cv_func_strtod_l=yes,
+        wx_cv_type_locale_t=yes,
-        wx_cv_func_strtod_l=no
+        wx_cv_type_locale_t=no
         )
         AC_LANG_POP()
     ])
 
-    if test "$wx_cv_func_strtod_l" = "yes" ; then
+    if test "$wx_cv_type_locale_t" = "yes" ; then
+        AC_DEFINE(wxUSE_XLOCALE)
+
         dnl We don't test (just) for locale_t existence, but we still define
         dnl this symbol to avoid changing the existing code using it.
         AC_DEFINE(HAVE_LOCALE_T)
+    else
+        AC_MSG_WARN([No locale_t support, wxXLocale won't be available])
     fi
 fi
 

include/wx/xlocale.h

@@ -41,7 +41,6 @@
         #define wxXLOCALE_IDENT(name) _ ## name
     #elif defined(HAVE_LOCALE_T)
         #include <locale.h>
-        #include <xlocale.h>
         #include <ctype.h>
         #include <stdlib.h>