New project bashrc_dispatch
Initial file from Joseph Wecker

Original location: <https://gist.github.com/3320963>.

NH discussion: <https://news.ycombinator.com/item?id=4369485>.
OS detection without launching external `uname` process
Avoid external processes in `shell_is_*` functions
Avoid unnecessary bashisms
Option to avoid exporting functions and variables
Move documentation to README
Make sure the anti-recursive checks behave well
Configuration/code separation
Unset variables just before exiting
Use `$OSTYPE` instead of `$MACHTYPE`

`$OSTYPE` is a better descriptor of the operating system. Let's not abuse
the content of `$MACHTYPE` that is meant to describe the architecture.
Walkthrough code comments
Initial from gist
Merge branch 'master' of https://github.com/gioele/bashrc_dispatch

Conflicts:
	bashrc_dispatch
update paths in readme
Contribution from bajsejohannes from hackernews
Added link in readme to hnews discussion
Added the missing ".bashrc_once"
Ensure that the startup scripts have access to the functions
don't recheck shell-platform if already set