Enable fully versioned binary archive creation

Set environment variable FULL_VERSION to enable creation of fully
versioned 2.1.x binary archives including patch level.

Starting with Ruby 2.1, release version follow a semantic versioning
scheme. Setting envar FULL_VERSION allows one to create binary
archives like `ruby-2.1.2-p117-i386-mingw32.7z` by invoking
`ruby21:package:archive`.
Use msys2(32bit) instead of old msys

Parallel make hangs due to msys bug.
http://sourceforge.net/p/mingw/bugs/1950/

msys2 is updated version of msys and the bug seems to be fixed.
http://mingw-users.1079350.n2.nabble.com/Status-of-MSYS2-td7582391.html

We pick up msys2 minimal dependencies to build ruby.
Need to set MSYSTEM=MINGW32 environment variable.

Default value of MSYSTEM is changed with msys2.
http://sourceforge.net/p/msys2/tickets/4/
Pass make options by MAKE_OPT environment variable

We can pass -jN to make for build speedup.
Replace mingw/gnuwin32 packages to msys2