file list fixed

src/CMakeLists.txt

 set (source_files
+   nxfile.cpp
+   nxwriter.cpp
+   ./impl/linux_nxfile.cpp
    lz4.cpp
    h5zlz4.cpp
-	 nxbuffer.cpp
-	 nxfile.cpp
    nxfinalizer.cpp
-	 nxwriter.cpp
+   nxbuffer.cpp
 )
 
 include_directories(