test_formats fails on non-x86_64

[opoplawski]

aarch64:

    Start 100: test_formats.pro
100: Test command: /builddir/build/BUILD/gdl-1.1.2-build/gdl-unstable-7c9b91a/build/src/gdl "-quiet" "-e" "if execute('test_formats') ne 1 then exit, status=1"
100: Working Directory: /builddir/build/BUILD/gdl-1.1.2-build/gdl-unstable-7c9b91a/build/testsuite
100: Environment variables: 
100:  LC_COLLATE=C
100:  GDL_PATH=/builddir/build/BUILD/gdl-1.1.2-build/gdl-unstable-7c9b91a/testsuite/:/builddir/build/BUILD/gdl-1.1.2-build/gdl-unstable-7c9b91a/src/pro/
100:  GDL_STARTUP=
100:  IDL_STARTUP=
100: Test timeout computed to be: 3600
100: % Attempt to call undefined procedure: DLM_REGISTER
100: % Execution halted at: $MAIN$          
100: % Compiled module: TEST_FORMATS.
100: % Compiled module: GDL_IDL_FL.
100: % GDL_IDL_FL: Detected Software : GDL
100: % When using the RAN1 mode, be sure to keep the RAN1 and dSFMT seed arrays in separate variables.
100: multiple reference file <<formats.GDL>> found ! First used !!
100: /builddir/build/BUILD/gdl-1.1.2-build/gdl-unstable-7c9b91a/build/testsuite/formats.GDL
100: /builddir/build/BUILD/gdl-1.1.2-build/gdl-unstable-7c9b91a/testsuite/formats.GDL
100: Files to be compared : formats.IDL, formats.GDL
100: % Compiled module: BANNER_FOR_TESTSUITE.
100: % TEST_FORMATS: ======================================================
100: % TEST_FORMATS: =                                                    =
100: % TEST_FORMATS: =  365 errors encountered during TEST_FORMATS tests  =
100: % TEST_FORMATS: =                                                    =
100: % TEST_FORMATS: ======================================================
3/4 Test #100: test_formats.pro .................***Failed    0.64 sec

ppc64le/s390x:

100: % TEST_FORMATS: =  1460 errors encountered during TEST_FORMATS tests  =

[GillesDuvert]

see #1881

I do not see how to avoid the 'rounding' vagaries btw different architectures.
Our tests are to avoid regressions, but porting to another architecture is another story. Very probably, it will mean adapting our test to the change of architecture, not to patch the code (if that was ever possible).