win32.c: suppress warning

* win32/win32.c (set_env_val): get rid of intger overflow warning by
  VC 11.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32.c: fix type

* win32/win32.c (constat_attr): fix type of attributes.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39535 b2dd03c8-39d4-4d8f-98ff-823fe69b080e