Merge branch 'fix-autoconf' into 'master'

Fix autoconf warnings for version 2.70

See merge request !113
7 jobs for master in 24 minutes and 53 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Prep
passed #6789103
fedora image

00:00:31

 
  Test
passed #6789104
fedora autotools build

00:24:22

passed #6789105
fedora meson build

00:00:30

passed #6789108
meson android arm64 fedora

00:02:03

passed #6789109
gst-macos-10.15
meson macOS

00:04:12

passed #6789106
docker windows 1809
meson vs2017 amd64

00:03:42

passed #6789107
docker windows 1809
meson vs2017 x86

00:03:39