[gdal-dev] Add capability to safely link against an external libtiff (3.X) and a GDAL build with internal libtiff (4.0) support

[Even Rouault]

> Even, all tests i performed (ubuntu 11.04 only) passed successfully so I
> can confirm that the patch works.

Great

> 
> My only concern is that I'm not able to reproduce the crash in cases in
> which GDAL is built without symbol renaming.

Hum, did you activate --with-hide-internal-symbols ? I somehow remember that 
it paradoxically helped revealing the duplicate symbol issues.