* regint.h (PLATFORM_UNALIGNED_WORD_ACCESS): Power PC does not
	  allow unaligned word access.

	* st.c (UNALIGNED_WORD_ACCESS): x86_64 allows unaligned word
	  access as well as i386.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@34565 b2dd03c8-39d4-4d8f-98ff-823fe69b080e