Log Message:
poppler*: update to 21.09.0

Release 21.09.0:
        core:
         * Splash: Massive spped improvement on files that use lots of \ 
save/restore (q/Q) operators
         * Correct decoding of signature properties Reason & Location when \ 
they are Unicode
         * Fix issues with malformed files
         * MSVC build fixes

        build system:
         * Call cmake_minium_required() before project()
         * Always append to CMAKE_{C,CXX}_FLAGS_${CMAKE_BUILD_TYPE}
         * correctly forward user-provided flags to try_compile()

Release 21.08.0:
        core:
         * Add API to allow addition and modification of outlines into a PDF
         * Use additional samples to test for constant parts of an axial gradient
         * forms: Create fallback fonts for some well known font names
         * Support reading the PDF Version from the Catalog
         * Fix XRef::copy when there are modified objects
         * Take into account that Date string may be in unicode
         * JBIG2Stream: Fix regression in "Do not consider a size-0 to be \ 
an error"
         * Replace a local bubble sort implementation by std::sort
         * Fix issues with malformed files

        build system:
         * Better error message when libjpeg is not found
         * Better error messages when libopenjpeg2 is not found

        qt5/qt6:
         * Document that a document has to outlive its pages
         * Make getPdfVersion return a dedicated version object

        glib:
         * mimick TextSelectionDumper logic change for spaceAfter