vm_eval.c: fix argument type

* vm_eval.c (eval_string_from_file_helper): fix callback argument
  type.  rb_protect passes a VALUE not a pointer.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42222 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
mkmf.rb: expand all macros

* lib/mkmf.rb (xsystem): expand environment variable in all macros not
  expanded with RbConfig.  [Bug #8702]
* test/mkmf/test_framework.rb (create_framework): replace all $@ not
  only once.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42223 b2dd03c8-39d4-4d8f-98ff-823fe69b080e