Remove TSLength from runtime header

Refactor node functions now that character offset and byte offset are stored separately

include/tree_sitter/parser.h

@@ -16,6 +16,11 @@ typedef struct TSTree TSTree;
 
 typedef unsigned short TSStateId;
 
+typedef struct {
+  size_t bytes;
+  size_t chars;
+} TSLength;
+
 typedef struct {
   bool visible : 1;
   bool named : 1;