configuration bug

[Issac Trotts]

I'm trying to compile GiNaC on a PC running Windows 2000
with the Cygwin UNIX utilities, but there seems to be a problem
with the directories.  When I compile CLN and make install,
the CLN files get installed in /usr/local/lib and /usr/local/include
by default.  This seems like a sensible place to put the files,
but when I run ./configure in the GiNaC directory, it tells me

configure: error: cannot find header for Bruno Haible's CLN

This message goes away if I install the CLN files in /usr/include
and /usr/lib, but I don't like to do it this way.  Do you know how
I can make the configure script look for the CLN files in their
default location in /usr/local?  

Thanks,
Issac