Move win/mac installation files to common dir. Split iss files.
Inno setup files are now three files: One for each 32 bit and 64 bit,
and a generic one included by the other two. This avoids having
to toggle 32 vs 64 bit settings each time.
(cherry picked from commit 2ae0a9568a5ef4a32958c11d27d32799376a1eac)
(cherry picked from commit 71ec55753cdca5fc06120070c899645ea0d08c91)