Use shared support folder for executables (gdiff, 64aadbd)

Using the shared support folder rather than the localizable resources folder should be more secure as it reduces the number of possible sites in which an attacker could substitute a hostile binary.

As noted elsewhere in the source, these types of security measures are an unwinnable battle; basically any application that runs with elevated privileges should be considered vulnerable of other users have write access to any part of it. Despite this, a "defense in depth" strategy suggests that plugging these minor holes is still a worthwhile idea, especially when the effort of doing so is minimal.

Signed-off-by: Greg Hurrell <greg@hurrell.net>