- Add special symbology-specific escape sequences (Code 128 only)

for manual Code Set switching via `input_mode` flag
  `EXTRA_ESCAPE_MODE` (CLI `--extraesc`) (ticket #204)
- GUI: disable "Reset" colour if default; add "Unset" to Printing
  Scale dialog (allows unsetting of X-dim/resolution settings
  without having to zap)
- library: guard against out-of-bounds rows (negative)
- test suite: fix some clang-tidy warnings; slight coverage
  improvements

docs/zint.1.pmd

@@ -1,6 +1,6 @@
 % ZINT(1) Version 2.12.0.9
 %
-% December 2022
+% January 2023
 
 # NAME
 
@@ -148,6 +148,11 @@ Paintbrush (`PCX`), Portable Network Format (`PNG`), Scalable Vector Graphic (`S
         \UNNNNNN (U+NNNNNN)     Any 21-bit Unicode character
                                 where NNNNNN is hexadecimal
 
+`--extraesc`
+
+:   Process the special escape sequences `\^A`, `\^B` and `\^C` that allow manual switching of Code Sets (Code 128
+    only). The sequence `\^^` can be used to encode data that contains special escape sequences.
+
 `--fast`
 
 :   Use faster if less optimal encodation or other shortcuts (affects Data Matrix, MicroPDF417, PDF417, QRCODE & UPNQR
@@ -506,7 +511,7 @@ ISO/IEC 18004:2015, ISO/IEC 23941:2022, AIM ITS/04-023 (2022)
 
 # COPYRIGHT
 
-Copyright © 2022 Robin Stuart. Released under GNU GPL 3.0 or later.
+Copyright © 2023 Robin Stuart. Released under GNU GPL 3.0 or later.
 
 # AUTHOR