Revert "reduce symbol visibility in sw"

Revert "reduce symbol visibility in sw"

This reverts commit 1a6711276f0c8abeb0028a47cc345a7453374a38.

After some discussion and experiments, it turned out this rather
fundamentally breaks clang's PCH build. Conclusion was: this change is
not significant enough to warrant making life harder for developers.

Excerpt of errors (affected were vbaswobj, msword & swui libs):

- ld.lld: error: undefined symbol: SwFormat::~SwFormat()
  >>> referenced by fmtcol.hxx:37 (sw/inc/fmtcol.hxx:37)
  >>>               core/workdir/CxxObject/sw/inc/pch/precompiled_vbaswobj.o:(SwFormatColl::~SwFormatColl())
- ld.lld: error: undefined symbol: SwFrameFormat::SetPositionLayoutDir(short)
  >>> referenced by precompiled_msword.cxx
  >>>               core/workdir/CxxObject/sw/inc/pch/precompiled_msword.o:(vtable for sw::SpzFrameFormat)
- ld.lld: error: undefined symbol: SwFrameFormat::SetLayoutDir(SwFrameFormat::tLayoutDir)
  >>> referenced by precompiled_swui.cxx
  >>>               core/workdir/CxxObject/sw/inc/pch/precompiled_swui.o:(vtable for sw::SpzFrameFormat)

Change-Id: I1dcf115cc191b1ebf1f8d5023c0c5015f891287a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167549
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <thorsten.behrens@allotropia.de>