vm.c: avoid inadvertent pin-down

* vm.c (vm_stat): get rid of inadvertent dynamic symbol 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
signal.c: preserve encoding

* signal.c (esignal_init): preserve encoding in error messages.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45483 b2dd03c8-39d4-4d8f-98ff-823fe69b080e