Implementation of name mangling algorithm.

This has to ensure that file names are unique among all files in an iso 
directory. Current implementation can be improved by using a hash table 
to keep the names, instead of iterate over all children. An alternative 
method, keeping children sorted all the time, thus allowing binary 
search, has been considered but discarded.                          

Current implementation support up to 9,999,999 equal files per 
directory.

src/error.h

@@ -36,6 +36,8 @@
 #define ISO_FILE_IS_NOT_DIR				-108
 #define ISO_FILE_IS_NOT_SYMLINK			-109
 
-#define ISO_CHARSET_CONV_ERROR           -150
+#define ISO_CHARSET_CONV_ERROR          -150
+
+#define ISO_MANGLE_TOO_MUCH_FILES       -200
 
 #endif /*LIBISO_ERROR_H_*/