This commit moves IO#readline to Ruby. In order to call C functions, keyword arguments must be converted to hashes. Prior to this commit, code like `io.readline(chomp: true)` would allocate a hash. This commits moves the keyword "denaturing" to Ruby, allowing us to send positional arguments to the C API and avoiding the hash allocation. Here is an allocation benchmark for the method: ``` x = GC.stat(:total_allocated_objects) File.open("/usr/share/dict/words") do |f| f.readline(chomp: true) until f.eof? end p ALLOCATIONS: GC.stat(:total_allocated_objects) - x ``` Before this commit, the output was this: ``` $ make run ./miniruby -I./lib -I. -I.ext/common -r./arm64-darwin22-fake ./test.rb {:ALLOCATIONS=>707939} ``` Now it is this: ``` $ make run ./miniruby -I./lib -I. -I.ext/common -r./arm64-darwin22-fake ./test.rb {:ALLOCATIONS=>471962} ``` [Bug #19890] [ruby-core:114803]