userenv: Implement DestroyEnvironmentBlock.

dlls/userenv/userenv.spec

 @ stdcall CreateEnvironmentBlock(ptr ptr long)
-@ stub DestroyEnvironmentBlock
+@ stdcall DestroyEnvironmentBlock(ptr)
 @ stdcall ExpandEnvironmentStringsForUserA(ptr str ptr long)
 @ stdcall ExpandEnvironmentStringsForUserW(ptr wstr ptr long)
 @ stdcall GetAllUsersProfileDirectoryA(ptr ptr)

dlls/userenv/userenv_main.c

@@ -65,6 +65,17 @@ BOOL WINAPI CreateEnvironmentBlock( LPVOID* lpEnvironment,
     return FALSE;
 }
 
+BOOL WINAPI DestroyEnvironmentBlock(LPVOID lpEnvironment)
+{
+    NTSTATUS r;
+
+    TRACE("%p\n", lpEnvironment);
+    r = RtlDestroyEnvironment(lpEnvironment);
+    if (r == STATUS_SUCCESS)
+        return TRUE;
+    return FALSE;
+}
+
 BOOL WINAPI ExpandEnvironmentStringsForUserA( HANDLE hToken, LPCSTR lpSrc,
                      LPSTR lpDest, DWORD dwSize )
 {