It exist cases where an external definition defined on a path is
malformed resulting in a parsing error from the official subversion
client.
In that case, externals defined on that path will not be processed
when exporting a revision.
(swh) anlambert@carnavalet:/tmp$ svn export https://svn.code.sf.net/p/modelbuilder/code@642 modelbuilder A modelbuilder A modelbuilder/src A modelbuilder/src/trunk A modelbuilder/src/trunk/contrib A modelbuilder/src/trunk/contrib/symbolic ... A modelbuilder/html/images/icon_linux.gif A modelbuilder/html/create.bat A modelbuilder/html/download.fp svn: E195005: Error parsing svn:externals property on '/tmp/modelbuilder/src/trunk/contrib': 'symbolic -r1288http://svn.freepascal.org/svn/fpcprojects/contrib/symbolic/'
So align loader behavior with official subversion client.
Fixes SWH-LOADER-SVN-7J