bin/in_place: diff: use --brief to avoid scanning the entire file for large files

bin/in_place: added $preserve_mtime flag

moved everything into /trunk/ to create the standard svn layout, for use with tools that require this (eg. git-svn). IMPORTANT: do NOT do an `svn up`. instead, re-use your working copy's existing files with `svn switch` (http://svnbook.red-bean.com/en/1.6/svn.ref.svn.c.switch.html).

bin/in_place: set the permissions of the new file to the original file when `chmod --reference` is available. this ensures that when a file is marked web-accessible, it stays web-accessible when you run an in_place command on it.

bin/in_place: don't run if no command to run, because that would erase the file

bin/in_place: use -e (exit on error) option to sh instead of adding `|| exit` after every command

in_place: Wrap EXIT handler in shell function so that "-escaping can easily be used on the temp file path

in_place: Documented that doesn't update file on error

Added in_place to run a stream command on a file