regex-tests: skip UTF-8 test on mingw

test-regex failed on mingw; and I traced it in gdb to an instance
of init_dfa() setting dfa->is_utf8 to 0 in spite of setlocale()
claiming success for "en_US.UTF-8".  test-wcwidth already has
precedent for skipping utf-8 tests where the system (or gnulib
setlocale replacement, in this case) lies about utf-8 support.

* modules/regex-tests (Depends-on): Add localcharset.
* tests/test-regex.c (main): Use it to skip test on mingw.

Signed-off-by: Eric Blake <eblake@redhat.com>

ChangeLog

@@ -1,3 +1,9 @@
+2013-03-12  Eric Blake  <eblake@redhat.com>
+
+	regex-tests: skip UTF-8 test on mingw
+	* modules/regex-tests (Depends-on): Add localcharset.
+	* tests/test-regex.c (main): Use it to skip test on mingw.
+
 2013-03-11  Eric Blake  <eblake@redhat.com>
 
 	tests: make it easier to bypass alarm time in debugger

modules/regex-tests

@@ -3,6 +3,7 @@ tests/test-regex.c
 tests/macros.h
 
 Depends-on:
+localcharset
 
 configure.ac:
 

tests/test-regex.c

@@ -26,6 +26,8 @@
 # include <signal.h>
 #endif
 
+#include "localcharset.h"
+
 int
 main (void)
 {
@@ -65,6 +67,11 @@ main (void)
           result |= 1;
       }
 
+      /* Check whether it's really a UTF-8 locale.
+         On mingw, the setlocale call succeeds but returns
+         "English_United States.1252", with locale_charset() returning
+         "CP1252".  */
+      if (strcmp (locale_charset (), "UTF-8") == 0)
         {
           /* This test is from glibc bug 15078.
              The test case is from Andreas Schwab in