Log Message:
poppler: Update to 0.81.0

pkgsrc changes:

to avoid adding a new dependency on boost, poppler now uses cairo as
the default graphics backend. the qt5 package seems to require splash (?)
so that one gets a new boost dependency.

we could also avoid it by forcing cmake detection to fail, but in this
case it prints a warning about performance losses.

Release 0.81.0:
        core:
         * Splash: Always enable support for CMYK rasterization
         * CairoOutputDev: Check scaled dimensions for 0. Issue #737
         * BaseCryptStream: Fix potential uninitialized memory read
         * SplashBitmap: Fix wrong width condition for splashModeDeviceN8
         * Fix crashes in malformed files

Release 0.80.0:
        core:
         * Annotations: Implement support for setting a different text in the \ 
appearance stream than the real text
         * Splash: Optionally use small_vector from boost
         * Fix memory leaks on broken files
         * Fix abort on broken files
         * Small code simplifications
         * Remove USE_FIXEDPOINT support. Issue #821

        qt5:
         * Fix MSVC build
         * Add subsitute-font information
         * Fix since marker of some functions
         * Fix leak when aborting text extraction
         * Small code simplifications

        glib:
         * Make print scaling getter visible
         * Make Duplex/NumCopies/PrintPageRange preference available in API
         * Implement Movie API

        utils:
         * pdftotext: Add -nodiag flag to remove diagonal text on output

        build system:
         * Mark external lib include dirs as SYSTEM