Make Integer#zero? a separated method and builtin (#3226)

A prerequisite to fix https://bugs.ruby-lang.org/issues/15589 with JIT.
This commit alone doesn't make a significant difference yet, but I thought
this commit should be committed independently.

This method override was discussed in [Misc #16961].

1 files changed, 1 insertions, 0 deletions

diff --git a/.document b/.document
index b18ca80971..0e0969a6d3 100644
--- a/.document
+++ b/.document
@@ -14,6 +14,7 @@ array.rb
 ast.rb
 dir.rb
 gc.rb
+integer.rb
 io.rb
 kernel.rb
 pack.rb