tree-sitter: vendor tree-sitter runtime

tree-sitter/tree-sitter commit 7685b7861ca475664b6ef57e14d1da9acf741275

Included files are:
lib/include/tree-sitter/*.h
lib/src/*.[ch]
LICENSE

src/tree_sitter/utf16.h

@@ -0,0 +1,21 @@
+#ifndef TREE_SITTER_UTF16_H_
+#define TREE_SITTER_UTF16_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <stdlib.h>
+#include "utf8proc.h"
+
+// Analogous to utf8proc's utf8proc_iterate function. Reads one code point from
+// the given UTF16 string and stores it in the location pointed to by `code_point`.
+// Returns the number of bytes in `string` that were read.
+utf8proc_ssize_t utf16_iterate(const utf8proc_uint8_t *, utf8proc_ssize_t, utf8proc_int32_t *);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // TREE_SITTER_UTF16_H_