gnu: libmpeg2: Fix build on armhf-linux.

* gnu/packages/patches/libmpeg2-arm-private-symbols.patch,
gnu/packages/patches/libmpeg2-global-symbol-test.patch: New files.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/video.scm (libmpeg2)[source](patches): New field.

gnu/packages/patches/libmpeg2-global-symbol-test.patch

@@ -0,0 +1,63 @@
+Rewrite the public symbol check to verify the shared libraries, to check for
+more things, and to avoid duplication; fixes make check on ARM
+
+Taken from Debian:
+https://salsa.debian.org/multimedia-team/mpeg2dec/blob/master/debian/patches/61_global-symbol-test.patch
+
+--- mpeg2dec.orig/test/globals
++++ mpeg2dec/test/globals
+@@ -1,4 +1,8 @@
+ #!/bin/sh
++# TODO
++# - fix checking of .a libs; problem is that "nm -g --defined-only" lists
++#   internal symbols; this can be solved by using objdump, but it's probably
++#   good enough to just run the tests on the shared lib
+ 
+ if test x"$srcdir" != x""; then
+     builddir="."	# running from make check, but it does not define that
+@@ -14,22 +18,30 @@ builddir=`cd $builddir;pwd`
+ 
+ error=0
+ 
+-bad_globals=`nm -g --defined-only $builddir/../libmpeg2/*.o |\
+-    awk '{if ($3) print $3}' | grep -v '^_\?mpeg2_'`
+-
+-if test x"$bad_globals" != x""; then
+-    echo BAD GLOBAL SYMBOLS:
+-    for s in $bad_globals; do echo $s; done
++# check_bad_public_symbols <symbol prefix> <lib file> [<lib file>...]
++#
++# checks public symbols in shared libs:
++# - allow prefix_anything
++# - reject _prefixanything
++# - allow _anything
++# - reject anything else
++#
++# NB: skips missing files
++check_bad_public_symbols() {
++    symbols_prefix="$1"
++    shift
++    lib_files=`ls "$@" 2>/dev/null`
++    [ -z "$lib_files" ] && return
++    bad_globals=`nm -g --defined-only $lib_files |
++        awk '{if ($3) print $3}' |
++        sed -n "/^${symbols_prefix}_/ d; /^_${symbols_prefix}/ { p; d }; /^_/ d; p"`
++    [ -z "$bad_globals" ] && return
+     error=1
+-fi
+-
+-bad_globals=`nm -g --defined-only $builddir/../libmpeg2/convert/*.o |\
+-    awk '{if ($3) print $3}' | grep -v '^_\?mpeg2convert_'`
++    echo BAD GLOBAL SYMBOLS in $lib_files:
++    echo "$bad_globals"
++}
+ 
+-if test x"$bad_globals" != x""; then
+-    echo BAD GLOBAL SYMBOLS:
+-    for s in $bad_globals; do echo $s; done
+-    error=1
+-fi
++check_bad_public_symbols mpeg2 $builddir/../libmpeg2/.libs/libmpeg2.so
++check_bad_public_symbols mpeg2convert $builddir/../libmpeg2/convert/.libs/libmpeg2convert.so
+ 
+ exit $error