Drop feature test for dlopen()

With libtool being mandatory from 9.17 on, so is dlopen() (via libltdl).
79 jobs for !3625 with 1727-drop-use-of-featuretest-have-dlopen in 33 seconds (queued for 8 seconds)
latest detached
Status Job ID Name Coverage
  Autoconf
passed #1034420
amd64 linux
autoreconf

00:00:16

 
  Precheck
passed #1034422
amd64 linux
clang-format

00:00:15

canceled #1034423
amd64 linux
coccinelle

00:00:31

passed #1034424
amd64 linux
danger

00:00:12

passed #1034421
amd64 linux
misc

00:00:11

 
  Build
canceled #1034439
amd64 linux
clang:asan

00:00:09

canceled #1034443
amd64 linux
clang:buster:amd64

00:00:13

canceled #1034446
amd64 libvirt
clang:freebsd11:amd64

00:00:03

canceled #1034447
amd64 libvirt
clang:freebsd12:amd64

00:00:02

canceled #1034448
amd64 libvirt
clang:openbsd:amd64

00:00:02

canceled #1034441
amd64 linux
clang:tsan

00:00:08

canceled #1034425
amd64 linux
gcc:alpine3.12:amd64

00:00:08

canceled #1034438
amd64 linux
gcc:asan

00:00:10

canceled #1034430
amd64 linux
gcc:buster:amd64

00:00:13

canceled #1034426
amd64 linux
gcc:centos6:amd64

00:00:14

canceled #1034427
amd64 linux
gcc:centos7:amd64

00:00:14

canceled #1034428
amd64 linux
gcc:centos8:amd64

00:00:13

canceled #1034437
amd64 linux
gcc:focal:amd64

00:00:10

canceled #1034442
amd64 linux
gcc:mutexatomics

00:00:13

canceled #1034432
amd64 linux
gcc:out-of-tree

00:00:13

canceled #1034431
amd64 linux
gcc:sid:amd64

00:00:13

canceled #1034433
arm64 linux
gcc:sid:arm64

00:00:08

canceled #1034434
i386 linux
gcc:sid:i386

00:00:12

canceled #1034444
amd64 linux
gcc:softhsm2.4

00:00:13

canceled #1034445
amd64 linux
gcc:softhsm2.6

00:00:08

canceled #1034429
amd64 linux
gcc:stretch:amd64

00:00:13

canceled #1034440
amd64 linux
gcc:tsan

00:00:09

canceled #1034435
amd64 linux
gcc:tumbleweed:amd64

00:00:11

canceled #1034436
amd64 linux
gcc:xenial:amd64

00:00:11

canceled #1034449
amd64 windows
msvc:windows:amd64

00:00:28

 
  Unit
canceled #1034463
amd64 linux
unit:clang:asan

canceled #1034467
amd64 linux
unit:clang:buster:amd64

canceled #1034470
amd64 libvirt
unit:clang:freebsd11:amd64

canceled #1034471
amd64 libvirt
unit:clang:freebsd12:amd64

canceled #1034465
amd64 linux allowed to fail
unit:clang:tsan

canceled #1034450
amd64 linux
unit:gcc:alpine3.12:amd64

canceled #1034462
amd64 linux
unit:gcc:asan

canceled #1034455
amd64 linux
unit:gcc:buster:amd64

canceled #1034451
amd64 linux
unit:gcc:centos6:amd64

canceled #1034452
amd64 linux
unit:gcc:centos7:amd64

canceled #1034453
amd64 linux
unit:gcc:centos8:amd64

canceled #1034461
amd64 linux
unit:gcc:focal:amd64

canceled #1034466
amd64 linux
unit:gcc:mutexatomics

canceled #1034456
amd64 linux
unit:gcc:sid:amd64

canceled #1034457
arm64 linux
unit:gcc:sid:arm64

canceled #1034458
i386 linux
unit:gcc:sid:i386

canceled #1034468
amd64 linux
unit:gcc:softhsm2.4

canceled #1034469
amd64 linux
unit:gcc:softhsm2.6

canceled #1034454
amd64 linux
unit:gcc:stretch:amd64

canceled #1034464
amd64 linux allowed to fail
unit:gcc:tsan

canceled #1034459
amd64 linux
unit:gcc:tumbleweed:amd64

canceled #1034460
amd64 linux
unit:gcc:xenial:amd64

 
  System
canceled #1034485
amd64 linux
system:clang:asan

canceled #1034489
amd64 linux
system:clang:buster:amd64

canceled #1034492
amd64 libvirt
system:clang:freebsd11:amd64

canceled #1034493
amd64 libvirt
system:clang:freebsd12:amd64

canceled #1034487
amd64 linux allowed to fail
system:clang:tsan

canceled #1034472
amd64 linux
system:gcc:alpine3.12:amd64

canceled #1034484
amd64 linux
system:gcc:asan

canceled #1034477
amd64 linux
system:gcc:buster:amd64

canceled #1034473
amd64 linux
system:gcc:centos6:amd64

canceled #1034474
amd64 linux
system:gcc:centos7:amd64

canceled #1034475
amd64 linux
system:gcc:centos8:amd64

canceled #1034483
amd64 linux
system:gcc:focal:amd64

canceled #1034488
amd64 linux
system:gcc:mutexatomics

canceled #1034478
amd64 linux
system:gcc:sid:amd64

canceled #1034479
arm64 linux
system:gcc:sid:arm64

canceled #1034480
i386 linux
system:gcc:sid:i386

canceled #1034490
amd64 linux
system:gcc:softhsm2.4

canceled #1034491
amd64 linux
system:gcc:softhsm2.6

canceled #1034476
amd64 linux
system:gcc:stretch:amd64

canceled #1034486
amd64 linux allowed to fail
system:gcc:tsan

canceled #1034481
amd64 linux
system:gcc:tumbleweed:amd64

canceled #1034482
amd64 linux
system:gcc:xenial:amd64

 
  Docs
canceled #1034494
amd64 linux
docs

00:00:05

 
  Postcheck
canceled #1034498
amd64 linux
cppcheck

00:00:03

canceled #1034495
amd64 linux
flake8

00:00:05

canceled #1034496
amd64 linux
pylint

00:00:05

canceled #1034497
amd64 linux
scan-build

00:00:04