rename `ZINT_CAP_EXTENDABLE` -> `ZINT_CAP_EANUPC`
(`ZINT_CAP_EXTENDABLE` marked as legacy)
CODE128: increase no. symbol chars max 60 -> 99
EAN-2/EAN-5: fix `BARCODE_BIND_TOP/BIND/BOX` output
GS1_128: warn if data > 48 (GS1 General Specifications max)
common: `is_extendable()` -> `is_ucpean()`
raster: add `ZFONT_HALIGN_CENTRE/LEFT/RIGHT` flags and process
in `draw_string()` (for drawing EAN/UPC outside digits), and
for `ZFONT_HALIGN_CENTRE` round when calculating centre
(shifts some texts 1 pixel left)
raster/vector: use offsets into `symbol->text` for EAN/UPC
instead of `out_upcean_split_text()` (removed)
BMP/EMF/GIF/PCX/PNG/PS/SVG/TIF: use new `out_colour_get_rgb()`
routine (replaces `colour_to_XXX()`)
general: simplify/fix some `error_number` handling/returning
frontend: truncate overlong `--primary` instead of ignoring;
negative floating pt option (for `--textgap`)
man page: list size detail for matrix symbols (`--vers`)
manual: further fiddling with scaling text; some typos
