informations from existing Makefile.
* ext/socket/extconf.rb: check if getaddrinfo() works fine only when
wide-getaddrinfo option is not given. fixed: [ruby-dev:25422]
* ext/tk/extconf.rb: separate tkutil configuration.
* lib/mkmf.rb ($extmk): check if under ext directory.
* lib/mkmf.rb (Logging.postpone): allow recursive operation.
* lib/mkmf.rb (try_constant): make sure if really a constant, reduce
the number of times of compile.
* lib/mkmf.rb (have_macro, have_var, byte_order): new functions.
* lib/mkmf.rb (find_library): allow directory list with separators.
* lib/mkmf.rb (arg_config): manage provided configuration options.
* lib/mkmf.rb (dir_config): accept arrays of directory names as
default values.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@7901 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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