upgrade to lcms2-2.6

Change-Id: Iaa5593d1593c9a54127c9019a4121af6a207d4c5
Reviewed-on: https://gerrit.libreoffice.org/9317
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Thomas Arnhold <thomas@arnhold.org>