.gitignore: ignore Xcode cruft

Signed-off-by: Steven Noonan <steven@uplinklabs.net>

Created by  Steven Noonan  on September 20, 2009
2GI42JV2BCREGJO3HDMQ4MXOIRWXUYHRC4K7TCWI753U5QHZD2AAC
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