--with-xerces won't accept a tree.

[warmerdam]

Dear Frank,

I very much appreciate your work on GDAL and Mapserver.

Sorry to bother you with this, but I until last summer, I
have had no problems with Mapserver and GDAL.
Now, I am having trouble when trying to include XML support
for Mapserver / GDAL through xerces-c (GDAL v 1.2.0a).

I am on Solaris 2.6, GCC 3.3.2, GNU make, Solaris ld, ...

The GDAL configure/build is currently not very intuitive to
me if you want xerces support. I managed to get everything
to compile using the following configure:

./configure --prefix=/data2/usr/local --with-gnu-ld=no --with-libz=internal
--with-png=internal --with-libtiff=internal --with-jpeg=internal
--with-gif=internal --with-geotiff=internal --with-gd=/data2/usr/local
--with-oci=no --with-xerces --with-xerces-inc="/data2/usr/local/include
-I/data2/usr/local/include/xercesc" --with-xerces-lib="-L/data2/usr/local/lib
-lxerces-c"

It would be useful if the parameters to include xerces only
took the install directory (in my case /data2/usr/local).

Frank says:
This bug is intended to address the final point, that the --with-xerces option 
should support providing a tree in which the xerces stuff has a normal
configuration.

[warmerdam]

OK, I have committed changes so that a
"configure --with-xerces=/data2/usr/local"

should automatically set the lib and include paths to /data2/usr/local/lib
and /data2/usr/local/include automatically.