Objectify: warn if Is{Component,Positional}ObjectRep absent #5795

Job	Run time
Test in OpenBSD	7m 40s
Cross compiler for s390x	27m 38s
testinstall - - ubuntu-latest	4m 34s
teststandard - - ubuntu-latest	19m 12s
testmanuals - - ubuntu-latest	5m 28s
testexpect testmockpkg testspecial test-compile testlibgap testkernel testworkspace - - ubuntu-latest	6m 54s
testpackages testinstall-loadall - - ubuntu-latest	25m 1s
makemanuals testmakeinstall - CONFIGFLAGS="--prefix=/tmp/gapprefix" NO_COVERAGE=1 - ubuntu-latest	5m 15s
teststandard - ABI=32 CONFIGFLAGS="" - ubuntu-20.04	18m 42s
testinstall - HPCGAP=yes ABI=64 - ubuntu-latest	7m 33s
testmockpkg testinstall - BOOTSTRAP_MINIMAL=yes - macos-latest	3m 38s
testbugfix - CONFIGFLAGS="--enable-memory-checking" - ubuntu-latest	26m 57s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=64 BUILDDIR=out-of-tree CONFIGFLAGS="--enable-valgrind" - ubuntu-latest	4m 38s
testbuildsys testmockpkg testinstall - NO_COVERAGE=1 ABI=32 BUILDDIR=out-of-tree CONFIGFLAGS="" - ubuntu-20.04	4m 48s
testinstall - JULIA=yes CONFIGFLAGS="--enable-debug" - ubuntu-20.04	4m 50s
testmockpkg testinstall - - windows-2019	15m 15s
Send Slack notification on status change	0s
	3h 8m 3s

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