* ext/readline/readline.c (Init_readline): Use rl_hook_func_t instead
of Function to support readline-6.3. (rl_hook_func_t is available
since readline-4.2.)
Reported by Dmitry Medvinsky. [ruby-core:61141] [Bug #9578]
* ext/readline/extconf.rb (rl_hook_func_t): define as Function for
very old readline versions. [ruby-core:61209] [Bug #9578]
* ext/readline/extconf.rb: fix typo, `$defs` not `$DEFS`.
[ruby-core:61756] [Bug #9578]
merge revision(s) r45225,r45240,r45488: [Backport #9578] [Backport #9630]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@45772 b2dd03c8-39d4-4d8f-98ff-823fe69b080e