...which contained the bulk of .cxx files that should logically go into
Library_pdfimport.  It was likely (only) used so that check_targets
CppunitTest_sdext_pdfimport, Executable_pdf2xml, and Executable_pdfunip could
access the library's internals without exporting them.  For the CppunitTest, use
the standard gb_CppunitTest_use_library_objects hack instead.  For the two
Executables, make that _use_library_objects hack available for Executables, too.
(It is a bit unclear whether those two Executables are really needed, they are
only referenced from the dead dmake-based
sdext/source/pdfimport/test/testdocs/makefile.mk and from vcl/README,
respectively; but just keep them alive for now.)

Change-Id: Ia2478508de216678be7a2302aba0c48f80de9d91
Reviewed-on: https://gerrit.libreoffice.org/20645Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>