DomainMapperTableManager::endOfRowAction(): valgrind warnings

Change-Id: I9e59ec2d45508d8f4dee8415411182576dacc45f
SwViewShell: fix brain-damaged non-virtual CalcLayout() override

The ooxml_export test crashes on Mac, because
SwModelTestBase::calcLayout() calls ViewShell::CalcLayout() and that
does not do StartAction(), and inside the layout indirectly a
StartAction()/EndAction() is then called, which of course trashes
the still-under-construction layout.

Strangely no crash on Linux, the layout is completely finished before
the SwModelTestBase::calcLayout() is called,
maybe because of the headless vclplug.

Change-Id: I767b1e41597ce752eb8c61dc106390f2abb90257
SwViewShell: try to catch errors of calling CalcLayout without action

Change-Id: I0352d543b7ce1ae6cd23d929ad5c9cbaeb1563bf
SwLayAction: there can be only one, so assert that

Requires tweaking the SwLayIdle code a bit, where an action is kept
alive a bit after it's done, which would trigger the assertion.

Change-Id: Ic5c8f90bc101b9d73cfde9691b2bbf405a001393