Architecture canonicalization fixes: * Lower-case the *_platform values to handle Pythons that return   upper-case values like 'AMD64'. * Add "i[456]86" entries to the canonicalization dictionary. * Sort and reformat the dictionary for readability.
Architecture canonicalization fixes:
* Lower-case the *_platform values to handle Pythons that return
  upper-case values like 'AMD64'.
* Add "i[456]86" entries to the canonicalization dictionary.
* Sort and reformat the dictionary for readability.

timj/scons,andrewyoung1991/scons,andrewyoung1991/scons,timj/scons,timj/scons,andrewyoung1991/scons,timj/scons,andrewyoung1991/scons,timj/scons,timj/scons,andrewyoung1991/scons,timj/scons,andrewyoung1991/scons,andrewyoung1991/scons,timj/scons,andrewyoung1991/scons,andrewyoung1991/scons,timj/scons