This is a preparation for [ruby-core:69892]
("io.c: avoid kwarg parsing in C API")
since I noticed ARGF.read_nonblock did not properly catch up to
the `exception: false' change.
* io.c (argf_read_nonblock): support `exception: false'
(io_nonblock_eof): new function
(io_read_nonblock): use io_nonblock_eof
(argf_getpartial): accept kwargs hash for `exception: false'
* test/ruby/test_argf.rb (test_read_nonblock): new test
[ruby-core:70000] [Feature #11358]
* NEWS: add item for ARGF.read_nonblock
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51285 b2dd03c8-39d4-4d8f-98ff-823fe69b080e