The motivation for remembering the text glyphs was to avoid repeated layout
calls during one sw layout run, this still preserves that optimization.

Approximate numbers for memory usage after importing the bugdoc finished:

- old: 401MB

- new 366MB (91% of baseline)

Change-Id: Ie960c606a8246c9c696745b2dcc9a49c3c570c07
Reviewed-on: https://gerrit.libreoffice.org/62496Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins