refactored write_syntax_tree_from_file. The function now uses mtree_from_iter function to write trees.
refactored write_syntax_tree_from_file.
The function now uses mtree_from_iter function to write trees.

niyaton/kenja-java-parser,yum-kvn/kenja,yum-kvn/kenja,niyaton/kenja,daiki1217/kenja,niyaton/kenja,daiki1217/kenja