epa_build: libharu: Add hpdf_namedict.h and hpdf_pdfa.h to the headers that are installed
epa_build: libharu: Add hpdf_namedict.h and hpdf_pdfa.h to the headers that are installed

This change in the CMake-based build system for libharu follows what
headers are installed in the autotools-based build system for libharu.
For some reason the lack of these installed headers did not cause issues for
my previous epa_builds, but they did cause issues for Andrew Ross's
recent epa_build.

Tested by Alan W. Irwin <airwin@users.sourceforge.net> on Linux using
an epa_build of libharu and plplot.  The result was the above headers
were install, and the test_noninteractive target worked fine in the
latter case (as it had done before).  Subsequent viewing of the pdf
results for each of the examples showed some long-standing (as far as
I can recall) rendering issues for the pdf device driver which have
now been documented at <https://sourceforge.net/p/plplot/bugs/155/>.

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot