v3.11.1

mogilefs-client 3.11.1

This release updates the IO#write garbage workaround to be
enabled for Ruby 2.0 and 2.1 users; but avoids it on the
just-released Ruby 2.4.1; as that includes the backported bugfix
for https://bugs.ruby-lang.org/issues/13085

There's also some trivial doc and code aesthetics fixes.

6 changes since 3.11.0:

      .olddoc.yml: add trailing slash on URL
      socket_common: expand IO#write garbage workaround to 2.0 and 2.1
      socket_common: limit garbage workaround to Ruby <= 2.4.1
      socket_common: remove needless 'o' modifier for Regexp
      socket_common: improve readability of case statement
      GNUmakefile: fix incorrect comment