[Zope-CMF] back-porting a GenericSetup fix to the 1.4 branch

[Rob Miller]

hi all,

currently, on the 1.4 branch of GenericSetup, there is what i consider to be a 
bug in the component registry import code.  the issue is that when you re-run 
the import step, even if you are not in purge mode, then any utilities that 
are registered with the given site manager will be replaced with brand new 
instances.  since local utilities are persistent objects, and often store 
important information within themselves, this seems to me a big enough issue 
to warrant a bug-fix on the 1.4 branch.

this appears to have been resolved on the trunk, as part of a bigger set of 
component registry improvements.  i've backported the changes (with minor 
adjustments to account for other version-related differences) to a local 1.4 
checkout, and have added a regression test that demonstrates the problem and 
verifies the fix.

if somebody feels strongly that this is too much of a functionality change for 
a maintenance branch, please respond here on-list... otherwise, i'll commit 
this to the 1.4 branch some time in the next day or so.

thanks!

-r