merge revision(s) 44474,44538,44539,44890,44896,45954: [Backport #8358]

	* configure.in: use SSE2 instructions for drop unexpected
	  precisions.  [ruby-core:54738] [Bug #8358]

	* configure.in: use SSE2 instructions to drop unexpected precisions on
	  other than mingw.  [ruby-core:59472] [Bug #8358]

	* configure.in: -mstackrealign is necessary for -msse2 working.
	  [ruby-core:54716] [Bug #8349]

	* configure.in: -mstackrealign is necessary for -msse2 working.
	  [ruby-core:54716] [Bug #8349]

	* configure.in: add qouting brackets and append wildcard for the
	  rest after target_cpu, to properly detect platform for SSE2
	  instructions.  [ruby-core:60576] [Bug #8358]

	* configure.in: Fix compilation error.
	  https://bugs.ruby-lang.org/issues/8358#note-16

	* configure.in: enable SSE2 on mingw. target='i386-pc-mingw32'.
	  [ruby-core:62095] [Bug #8358]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@46514 b2dd03c8-39d4-4d8f-98ff-823fe69b080e