Avoid collisions between parallel installations of Cygwin

[Charles Wilson]

Corinna wrote:
> Here are the questions.
> - Does anything speak against the idea of the patch?
> - Does anybody see a problem with the patch?
> - Anything else?

I think it's great. I have found it SO useful to have both a cygwin-1.5
and a cygwin-1.7 tree installed (e.g. when I break my 1.7 tree I can fix
it using familiar cygwin tools from the 1.5 installation, rather than
cmd.exe or explorer) -- and I've been able to do that because the
1.5/1.7 versions *mostly* don't interfere.

comments about the patch:

cygwin/external.cc [CW_GET_INSTKEY]: it's dangerous to rely on the
fall-thru behavior to 'default: break;' if somebody adds another case.
Use an explicit break; statement.

cygwin/shared.cc: The first big comment block appears incomplete: "Thus,
different Cygwin installations generate different object names and so
are"....are what?

Should cygcheck be modified to print out the installation_key?

--
Chuck