ENH: Rename Windows "Start menu" entry for 32 and 64-bit install

As discussed during April 8th 2014 developer hangout, considering that
64-bit build are now the default, the associated start menu entries are
renamed so that a suffix is instead associated with the 32-bit start menu
entry instead of the 64-bit one:

 Slicer 4.3.1 [...] (Win64) -> Slicer 4.3.1 [...]

 Slicer 4.3.1 [...] -> Slicer 4.3.1 [...] (Win32)

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23063 3bd1e089-480b-0410-8dfb-8563597acbee