sw: fix htmlexport test failure

Somehow this test failed on Windows, because of restoring a "NONE" field
unit to SW_MOD()... apparently the "charborder.odt" test is run first,
and preTest() sees a null SW_MOD() then postTest restores a NONE metric.

Hack around that by calling SwGlobals::ensure() to create SW_MOD().

Change-Id: I6c0cda3aae397071bca16bf0e5d9f8105635550f
sw: why is swdll.hxx included everywhere?

Change-Id: Ic401ca83666a887be9e5efe8369440e78fa4eeac
Revert "sw: _one_ unit test with use_library_objects sw ought to be enough"

This reverts commit d2a4e7c7f70a0ff0769ed228320833fa6b29bff9.

We now export SwGlobals::ensure for another test, so no need to use
sw objects in this one...
sw: the tox test can now use the exported SwGlobals::ensure()

Change-Id: Ibb4defec621fe479a877248a970eac15916ec6ec