Add our implementation for wcscoll() and wcsxfrm().

* add Wcscoll() and Wcsxfrm() ICU locale backend
* provide implementations of wcscoll() and wcsxfrm() that are using
  the respective methods of the locale backend

headers/private/libroot/locale/ICUCollateData.h

@@ -29,6 +29,10 @@ public:
 			status_t			Strcoll(const char* a, const char* b, int& out);
 			status_t			Strxfrm(char* out, const char* in, size_t size,
 									size_t& outSize);
+			status_t			Wcscoll(const wchar_t* a, const wchar_t* b,
+									int& out);
+			status_t			Wcsxfrm(wchar_t* out, const wchar_t* in,
+									size_t size, size_t& outSize);
 
 private:
 			status_t			_ToUnicodeString(const char* in,

headers/private/libroot/locale/ICULocaleBackend.h

@@ -61,6 +61,10 @@ public:
 	virtual	status_t			Strcoll(const char* a, const char* b, int& out);
 	virtual status_t			Strxfrm(char* out, const char* in, size_t size,
 									size_t& outSize);
+	virtual	status_t			Wcscoll(const wchar_t* a, const wchar_t* b,
+									int& out);
+	virtual status_t			Wcsxfrm(wchar_t* out, const wchar_t* in,
+									size_t size, size_t& outSize);
 
 	virtual status_t			TZSet(const char* timeZoneID, const char* tz);
 	virtual	status_t			Localtime(const time_t* inTime,

headers/private/libroot/locale/LocaleBackend.h

@@ -144,6 +144,10 @@ public:
 									int& out) = 0;
 	virtual status_t			Strxfrm(char* out, const char* in, size_t size,
 									size_t& outSize) = 0;
+	virtual	status_t			Wcscoll(const wchar_t* a, const wchar_t* b,
+									int& out) = 0;
+	virtual status_t			Wcsxfrm(wchar_t* out, const wchar_t* in,
+									size_t size, size_t& outSize) = 0;
 
 	virtual status_t			TZSet(const char* timeZoneID,
 									const char* tz) = 0;