Locale: fix binary compatibility for BNumberFormat

Issue: https://github.com/HaikuArchives/Album/issues/15
Change-Id: I1f8d5055f929957adb0cca20a8f6b13bcccabfab
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3807
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

headers/os/locale/NumberFormat.h

@@ -44,6 +44,7 @@ public:
 			BString				GetSeparator(BNumberElement element);
 
 private:
+								BNumberFormat();
 								BNumberFormat(const BNumberFormat &other);
 
 private:

src/kits/locale/NumberFormat.cpp

@@ -193,6 +193,13 @@ BNumberFormat::BNumberFormat(const BLocale* locale)
 }
 
 
+BNumberFormat::BNumberFormat()
+	: BFormat()
+{
+	fPrivateData = new BNumberFormatImpl();
+}
+
+
 BNumberFormat::BNumberFormat(const BNumberFormat &other)
 	: BFormat(other)
 {