Improve parsergen & scannergen to have better quick guide experience.

1. 🆕 Add Quick Guide to README.md
2. 🆕 Add version number to the banner of every generated C++ file.
3. 🆕 example/MinLang/README.md
4. ✍️ Obsolete scannergen option %CPP_INCLUDE
5. ✍️ Default parser class name when absent.
6. ✍️ GLR context support is complete. It has been broken for a long time.
7. ✍️ Default %CHAR_TYPE to bux::C_LexUTF32
8. ✍️ Legacy code mildly modernized.
9. ✍️ Encourge to add RE_Suite.txt as scannergen argument instead of using #include "RE_Suite.txt" and -I flag.
   (All grammar.txt & reparse scripts changed!)
10. ✍️ All example parsers re-generated.
11. ✍️ Package desc & version number source in PKGBUILD

Upgrade according to bux's changes

1. ✍️ Update according to bux v1.1.1
2. ✍️ Move parser POC example to aur_poc/ subdir. …
3. ✍️ Port PKGBUILD to cloning from the tags.