Reenable SSE2 for QCMS on Win64.

Note that the SSE1 code is left out since MSVC doesn't support the particular __m64 MMX intrinsics it uses:
http://msdn.microsoft.com/en-us/library/08x3t697.aspx

BUG=179657

Review URL: https://codereview.chromium.org/185743003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256183 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256183