Some misc Documentation patches

The result of me playing around with git format-patch and git-am.

builtin-log.c: Fix typo in comment Found while searching for the omnious --mbox option

Documentation: format-patch has no --mbox option
Replace --mbox with --stdout. Probably needs some more
thought to really improve the documentation

git-am: Clean up the asciidoc documentation Fixing some things that annoyed me while reading the man page and some things that I found while fixing the former. If I should split that in more than one patch, please say so.

 Documentation/git-am.txt        |   38 ++++++++++++++++++++------------------
 Documentation/git-applymbox.txt |    2 +-
 Documentation/git-mailinfo.txt  |    3 +--
 builtin-log.c                   |    3 +--
 4 files changed, 23 insertions(+), 23 deletions(-)