Ruby » Ruby master

• io.c (io_fread, io_getpartial, rb_io_sysread): set buffer size
  after check if readable, which can cause thread switch.
  [ruby-dev:45297][Bug #6099]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@34846 b2dd03c8-39d4-4d8f-98ff-823fe69b080e