vm.c: avoid inadvertent pin-down
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45482 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
vm.c: avoid inadvertent pin-down
and preserve encoding in error messages. also should not use
RSTRING_PTR macro on function calls.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45482 b2dd03c8-39d4-4d8f-98ff-823fe69b080e