thread_win32.c: suppress warning

* thread_win32.c (native_sleep): constify local variable to suppress a
  false positive might-be-clobbered warning.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39523 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32.c: suppress warnings

* win32/win32.c (set_env_val): reuse size of typedef to suppress
  unused-local-typedefs warnings from gcc 4.8 and reduce same
  calculation.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39524 b2dd03c8-39d4-4d8f-98ff-823fe69b080e