- unified bashStatement, kshStatement and shStatement as much as
possible
- separated builtin commands from external programs
- cleaned up kornshell flavor logic
- fixed alias syntax highlighting
- added test for bash alias syntax highlighting
- removed daemon keyword
closes: vim/vim#1835511bde1f169
Co-authored-by: Bjoern Foersterling <bjoern.foersterling@gmail.com>