* include/ruby/defines.h, siphash.c, st.c (UNALIGNED_WORD_ACCESS):
  add PowerPC64 too, which is capable to access unaligned words.
  patched by Gustavo Frederico Temple Pedrosa in [ruby-core:63937].
  [Feature #10081]
* regint.h (PLATFORM_UNALIGNED_WORD_ACCESS): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46915 b2dd03c8-39d4-4d8f-98ff-823fe69b080e