Fix my mail signature command again

If I define it within the use-package call for Markdown Mode then it
doesn’t have any effect.  And my previous idea to do it in Mail Mode
was stupid because it has no access to the ‘markdown-mode-map’ table.
This patch defines my signature function outside the scope of all
packages so that I can bind it within the setup for Markdown Mode.
Add a snippet for creating new scsh scripts
Slightly improve the indentation

This patch only changes whitespace.
Use the Autopair minor mode
Use Linux-style indentation as my default CC Mode style