dir.c: fix conditions for ALPHA

* dir.c (has_magic): return ALPHA at alphabetical name regardless
  FNM_CASEFOLD flag.
* dir.c (glob_helper): fix conditions for ALPHA.
  [ruby-core:61552] [Bug #9648]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45967 b2dd03c8-39d4-4d8f-98ff-823fe69b080e