chore, elevate clang bug work around in leaps_before() to clang >= 3.3

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/clang'

* bld/clang:
  chore, elevate clang bug work around in leaps_before() to clang >= 3.3
minor, refactor proc_line() logic, exit early

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, provide -v|--invert-match to dgrep(1)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
test, provide regression tests for dgrep -v|--invert-match

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'cmd/dgrep'

* cmd/dgrep:
  test, provide regression tests for dgrep -v|--invert-match
  minor, provide -v|--invert-match to dgrep(1)
  minor, refactor proc_line() logic, exit early