Fix integer size of subtree's child count field
Fix integer size of subtree's child count field

Fixes tree-sitter/tree-sitter-cpp#175

tree-sitter/tree-sitter,tree-sitter/tree-sitter,tree-sitter/tree-sitter,tree-sitter/tree-sitter,tree-sitter/tree-sitter,tree-sitter/tree-sitter,tree-sitter/tree-sitter