Refactor generated parsers to used explicit table

This is slightly slower than encoding the parse table in
flow control, but allows the parser to inspect the parse
table more flexibly. This is needed for incremental parsing.

src/runtime/stack.c

@@ -28,7 +28,7 @@ state_id ts_stack_top_state(const ts_stack *stack) {
     return stack->entries[stack->size - 1].state;
 }
 
-ts_tree * ts_stack_root(ts_stack *stack) {
+ts_tree * ts_stack_root(const ts_stack *stack) {
     return stack->entries[0].node;
 }