Need to require ack-and-a-half for it to work

I guess I didn't test this as well as I should have previously. It would
appear that defvar without a value still leaves it as void. Since the
function references the arguments before autoload brings in
ack-and-half, it's used in projectile while still void.
Fix git-grep to work in Windows.
Merge pull request #273 from bling/master

Fix git-grep to work in Windows.
Merge pull request #276 from dgtized/fix-ack-for-real

Need to require ack-and-a-half for it to work
Fix build
Really fix the build
Revert "Fix a typo"

This reverts commit 4fda4ad9166bfeb5e19016afe967c72ea4899dc7.
Comment a tricky bit of code