QRCODE: use stricter interpretation of ZINT_FULL_MULTIBYTE, excluding
certain trailing bytes
libzint: fix some confusing error messages introduced by segment stuff
general: new escape chars \U, \d and \o
backend_qt: fudge rendering of border rectangles due to scaling/translation
rounding errors TODO: better fudge
GUI: foreground/background colours -> text boxes and icon buttons, add swap
button, independently movable picker (NULL parent), preview colour changes,
preview Data Window changes, add clear data (del) buttons, add zap button
and Factory Reset menu option, various other fixes
libzint: remove STATIC_UNLESS_ZINT_TEST, use wrappers
CMake: add find package QtSvg, remove QtXml
manual: split symbology and general specs and sort, move DAFT to 4-state,
UPC/EAN -> EAN/UPC, DataBar -> GS1 DataBar always, expand MAILMARK info,
various other fiddlings
man page: options or -> |, expand MSI Plessey check digit options
README.linux: add packages info
license: add SPDX-License-Identifier to touched files
HANXIN/QRCODE: use Hanzi/Kanji modes when compatible ECIs given
manual: one true source now manual.pmd from which manual.txt is generated
CLI: man page moved from frontend/zint.1.gz to docs/zint.1.gz, now
generated from docs/zint.1.pmd
add README.linux to root dir
