ext/rbconfig/sizeof: move to an extension library

* common.mk, ext/rbconfig/sizeof: move RbConfig::SIZEOF to an
  extension library to get rid of annoying nmake VPATH rule.

* inits.c (rb_call_inits), miniinit.c (Init_sizes): RbConfig::SIZEOF
  is no loger built-in.

* template/sizes.c.tmpl (Init_sizeof): rename initialization function.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43708 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* properties.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43709 b2dd03c8-39d4-4d8f-98ff-823fe69b080e