scripts/functions: svn retrieval first tries the mirror for tarballs

The svn download helper looks for the local tarballs dir to see if it
can find a pre-downloaded tarball, and if it does not find it, does
the actual fetch to upstream via svn.

In the process, it does not even try to get a tarball from the local
mirror, which can be useful if the mirror has been pre-populated
manually (or with a previously downloaded tree).

Fake a tarball get with the standard tarball-download helper, but
without specifying any upstream URL, which makes the helper directly
try the LAN mirror.

Of course, if no mirror is specified, no URL wil be available, and
the standard svn retrieval will kick in.

Reported-by: ANDY KENNEDY <ANDY.KENNEDY@adtran.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

diff -durN ltrace-0.4.orig/configure ltrace-0.4/configure

--- ltrace-0.4.orig/configure	2008-10-23 23:19:38.000000000 +0200

+++ ltrace-0.4/configure	2008-10-23 23:19:06.000000000 +0200

@@ -1392,6 +1392,9 @@

 HOST_OS="$host_os"

+case "${HOST_OS}" in

+  linux-*) HOST_OS=linux-gnu;;

+esac

 ac_ext=c

diff -durN ltrace-0.4.orig/configure.ac ltrace-0.4/configure.ac

--- ltrace-0.4.orig/configure.ac	2008-10-23 23:19:43.000000000 +0200

+++ ltrace-0.4/configure.ac	2008-10-23 23:18:44.000000000 +0200

@@ -7,6 +7,9 @@

 dnl Check host system type

 AC_CANONICAL_HOST

 HOST_OS="$host_os"

+case "${HOST_OS}" in

+  linux-*) HOST_OS=linux-gnu;;

+esac

 AC_SUBST(HOST_OS)

 dnl Checks for programs.