Merge branch 'rs/grep-parseopt'

* rs/grep-parseopt:
  grep: make callback functions static
  grep: use parseopt
  grep: remove global variable builtin_grep
  parseopt: add PARSE_OPT_NODASH
  parseopt: add OPT_NUMBER_CALLBACK
  parseopt: add OPT_NEGBIT

diff --cc Documentation/technical/api-parse-options.txt
Simple merge