[DOC] NEWS entries for C APIs

[ko1]

compare with Ruby 3.2 and Ruby 3.3 libruby.so

ko1@WSL2 ~/ruby/build/trunk
$ objdump -T ../ruby_3_2/libruby.so | ruby -e 'r = []; ARGF.each_line{|l| r << [$1,$3] if /^[\da-f]+ (.{7}) (\S+).+\s(\S+$)/ =~ l and $2 != "*U
ND*" and !$3.start_with?("_")}; pp r.sort' > expo.3.2

ko1@WSL2 ~/ruby/build/trunk
$ objdump -T libruby.so | ruby -e 'r = []; ARGF.each_line{|l| r << [$1,$3] if /^[\da-f]+ (.{7}) (\S+).+\s(\S+$)/ =~ l and $2 != "*UND*" and !$3
.start_with?("_")}; pp r.sort' > expo.3.3

ko1@WSL2 ~/ruby/build/trunk
$ diff -u expo.3.2 expo.3.3 | x

[ioquatix]

This is great, nice work. Thanks for writing about the changes to io.h.