merge revision(s) 39484,39485: [Backport #7952]

	* thread.c: Document Thread::new, clean up ::fork and mention calling
	  super if subclassing Thread


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39703 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 39489,39490: [Backport #7950]

	* enc/depend (ARFLAGS): VisualC++ linker does not allow spaces between
	  output option and the output file name.  [Bug #7950]

	* enc/depend (RANLIB): set default command to do nothing, or make the
	  entire line a label on Windows.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39704 b2dd03c8-39d4-4d8f-98ff-823fe69b080e