added gitignore for C junk
added gitignore for C junk

copied from https://github.com/github/gitignore/blob/master/C.gitignore

wzwright/GroupDesignBattleship,GroupDesignBattleship/debian,wzwright/GroupDesignBattleship,GroupDesignBattleship/debian,wzwright/GroupDesignBattleship,GroupDesignBattleship/debian,wzwright/GroupDesignBattleship,GroupDesignBattleship/debian