extconf.rb: configure libffi first

* ext/fiddle/extconf.rb: configure libffi for the check requires
  the headers.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48917 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-12-22

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48918 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
extconf.rb: libffi with libruby

* ext/fiddle/extconf.rb: link libffi with libruby for symbols
  provided by ruby on some platforms, e.g. alloca.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48919 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
signal.c: fix received_signal

* signal.c (received_signal): fix condition to define.
  [ruby-core:67032] [Bug #10629]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48920 b2dd03c8-39d4-4d8f-98ff-823fe69b080e