The QLocale::C should not have a separator for thousands in numerical values

#include <locale.h>
#include <stdio.h>

int main(int argc, char *argv[]){
  setlocale(LC_ALL,"C");
  struct lconv *cconv = localeconv();
  printf("%s\n", cconv->thousands_sep);
  printf("%s\n", cconv->mon_thousands_sep);
  return 0;
}

#include <QtTest/QtTest>
#include <QLocale>

class Test : public QObject{
  Q_OBJECT

private slots:
  void testCLocaleThousandSeparator(){
    QCOMPARE(QLocale::c().toString(1000.0), QString::fromLatin1("1000"));
  }
  
};

QTEST_MAIN(Test)
#include "test.moc"

diff --git a/src/corelib/tools/qlocale.cpp b/src/corelib/tools/qlocale.cpp
index e670ad2..20c789b 100644
--- a/src/corelib/tools/qlocale.cpp
+++ b/src/corelib/tools/qlocale.cpp
@@ -2233,7 +2233,7 @@ QLocale::QLocale(Language language, Country country)
         p.numberOptions = default_number_options;
         p.index = localePrivateIndex(defaultPrivate());
     } else {
-        p.numberOptions = 0;
+        p.numberOptions = QLocale::OmitGroupSeparator;
         p.index = localePrivateIndex(d);
     }
 }