...as the default Point ctor already zero-initializes its members, remvoing the
need for some memset calls (that cause -Werror=class-memaccess, "clearing an
object of non-trivial type ‘class Point’" with upcoming GCC 8).  Other such
problematic memset calls are replaced with std::fill, which appears to produce
adequate code with recent compilers (looked at GCC 7.2 and 8, Clang 7, at -O2),
a tight loop of filling the memory with zeroes.

A follow-up commit might want to use unique_ptr or vector for pPointAry.

Change-Id: I566422b2213643ab762f0d87a25e745ec2f35ee4
Reviewed-on: https://gerrit.libreoffice.org/48488Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>