package/libmpeg2: switch to videolan Gitlab repository

The source code archives don't seem to be available anymore from the libmpeg2
website (Sourceforge) [1], and their SVN repository [2] doesn't seem
reachable either.

This fixes recent autobuilder failures, such as
https://autobuild.buildroot.net/results/ede/edeef6a480350880b12eebd94654644e43c2670e/

[1] https://libmpeg2.sourceforge.io/
[2] svn://svn.videolan.org/libmpeg2/trunk

Signed-off-by: Titouan Christophe <titouan.christophe@mind.be>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit 2f2a83fdc49de38148066ab1689411ce6e760bff)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

package/libmpeg2/libmpeg2.hash

@@ -1,3 +1,3 @@
 # Locally computed:
-sha256  dee22e893cb5fc2b2b6ebd60b88478ab8556cb3b93f9a0d7ce8f3b61851871d4  libmpeg2-0.5.1.tar.gz
+sha256  1b3adfb73e7d34ce9259130683d884b0b1af67572c9fd8229d45f55794b6dc0c  libmpeg2-v41f78cf4d30d0da0a24c8ecbc38b0c9dfd43f871.tar.gz
 sha256  32b1062f7da84967e7019d01ab805935caa7ab7321a7ced0e30ebe75e5df1670  COPYING

package/libmpeg2/libmpeg2.mk

@@ -5,7 +5,11 @@
 ################################################################################
 
 LIBMPEG2_VERSION = 0.5.1
-LIBMPEG2_SITE = http://libmpeg2.sourceforge.net/files
+# Gitlab repository does not have a 0.5.1 git tag,
+# use the corresponding commit sha instead
+LIBMPEG2_VERSION_SHA = 41f78cf4d30d0da0a24c8ecbc38b0c9dfd43f871
+LIBMPEG2_SOURCE = libmpeg2-v$(LIBMPEG2_VERSION_SHA).tar.gz
+LIBMPEG2_SITE = https://code.videolan.org/videolan/libmpeg2/-/archive/$(LIBMPEG2_VERSION_SHA)
 LIBMPEG2_LICENSE = GPL-2.0+
 LIBMPEG2_LICENSE_FILES = COPYING
 LIBMPEG2_INSTALL_STAGING = YES