tests/test-gpg.t

largefiles: improve comments, internal docstrings

- fix some ungrammatical/unclear/incorrect comments/docstrings
- rewrite some really unclear comments/docstrings
- make formatting/style more consistent with the rest of Mercurial
  (lowercase without period unless it's really multiple sentences)
- wrap to 75 columns
- always say "largefile(s)", not "lfile(s)" (or "big files")
- one space between sentences, not two

Test the GPG extension

  $ "$TESTDIR/hghave" gpg || exit 80
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > gpg=
  > 
  > [gpg]
  > cmd=gpg --no-permission-warning --no-secmem-warning --homedir $TESTDIR/gpg
  > EOF
  $ hg init r
  $ cd r
  $ echo foo > foo
  $ hg ci -Amfoo
  adding foo

  $ hg sigs

  $ hg sign 0
  Signing 0:e63c23eaa88a

  $ hg sigs
  hgtest                             0:e63c23eaa88ae77967edcf4ea194d31167c478b0

  $ hg sigcheck 0
  e63c23eaa88a is signed by:
   hgtest