by using ctor initializer list, removing redundant realloc
and other small tweaks

Change-Id: I73775ef3677244de5c04e8743c43228d6cb3b008
Reviewed-on: https://gerrit.libreoffice.org/27174Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>