swift234

[sil-extract] Add a simple test for sil-extract.

*NOTE* I know it may seem a little bit wasteful to have sil-extract included as
a pattern in lit, but I feel it is the right thing to do since it will cause lit
in the fail line to display the full path to sil-extract making it easier to
quickly copy/paste in the shell to fix any issues that may come up.

Swift SVN r11396