Factored initialisation of args into function init_args()
Added words to access command line parameters: `raw-argc`, `raw-argv`.
Removed internal variable args.progname.
Added `argc` and `argv`: words for program parameters.
Added pronunciations for the new words.
Renamed prefix 'strstream' to 'str'.
Added copy & fill words: `cmove` `fill` `erase`.
Renamed heads.c to headers.c.
Clarified definition of `erase`.