Initial support for low level ECMA-119 tree.

This only adds the tree creation functions, no sorting and name mangling 
yet. Only plain ECMA-119 supported for now, nor RR, relaxed 
restrictions, etc..

This also adds a little test program.

src/ecma119.h

@@ -10,9 +10,11 @@
 #define LIBISO_ECMA119_H_
 
 typedef struct ecma119_image Ecma119Image;
+typedef struct ecma119_node Ecma119Node;
 typedef struct Iso_File_Src IsoFileSrc;
 
 struct ecma119_image {
+    Ecma119Node *root;
     
     unsigned int iso_level:2;