The only change is that version support is now available
unconditionally, otherwise most code changes were bundled already in the
form of patches.

(cherry picked from commits b2b1debf and
14c91e12b5bb3444235e1444eeefab42e21e3cb5)

Conflicts:
	configure.ac
	external/libepubgen/libepubgen-epub3.patch.1
	writerperfect/source/writer/EPUBExportDialog.cxx
	writerperfect/source/writer/EPUBExportFilter.cxx

Change-Id: I0e456d85c9d84002cabcd77b31b02c9a7ad16ac5
Reviewed-on: https://gerrit.libreoffice.org/46440Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: David Tardon <dtardon@redhat.com>