[orbitcpp-list] patch for overriding idl backend dir as cmd parameter

[Phil d. <ph...@us...>]

Hi Elliot, Dick,

Here's a patch to allow the orbit-idl backend library directory to be
overridden as a command line parameter. 

We need this for ORBit-C++ because otherwise the package cant compile
its own tests without the user first installing its C++ backend library
(which rules out 'make distcheck').

The patch is against a snapshot of the ORBit CVS archive taken today
(9th March)

Cheers

Phil.