...which can be attractive for installation sets that use --with-system-poppler
but do not want the LO core package to depend on a poppler package.  See the
comment at the top of scp2/source/ooo/module_pdfimport.scp for details.

The build-time --disable-pdfimport configure switch is gone, PDF Import is built
unconditionally for all platforms but Android and iOS now.  (The
ENABLE_PDFIMPORT variable now uses TRUE/FALSE rather than YES/NO, to increase
consistency across those variables.)

Change-Id: I6509d0b2e770b276cd54540408fb1ec5a7dda058