Test that automake and meson have the same tests

This commit adds a new test. This test is a shell script that extracts
the lists of tests from Makefile.sources and meson.build and compares
them. The test fails if the two have different lists of tests.

The script does not check if the conditions for when a test is included
are the same. If anyone wants to add that, feel free. For a first
version of this script, just checking the list of files is hopefully
enough.

As with the other shell script based tests that we have (see src/*sh),
this test is only run by autotools.

Signed-off-by: Uli Schlachter <psychon@znc.in>
Status Job ID Name Coverage
  Prep
passed #6188711
fedora image

00:00:42

 
  Test
passed #6188712
fedora autotools build

00:24:13

passed #6188713
fedora meson build

00:00:39

passed #6188714
docker windows 1809
meson vs2017 amd64

00:05:38

passed #6188715
docker windows 1809
meson vs2017 x86

00:05:42