Grep 2.10 --include is broken

[jpmv27]

Wasted some time today struggling with trying to get vim-easygrep to work on a Ubuntu 12.04 box. Turns out this release has grep version 2.10, in which --include only works properly when -R option is also present (as far as I can tell.) Otherwise, it seems to work as --exclude.

Since vim-easygrep depends so much on --include in some modes, would it be worthwhile to add a test for this buggy version and warn the user?