Xcode: Coalesce multiple "copies" sections in the same target with the same
"destination" property into the same PBXCopyFilesBuildPhase.

TEST=gyptest.py test/copies/gyptest-samedir.py
Review URL: https://codereview.chromium.org/12088112

git-svn-id: http://gyp.googlecode.com/svn/trunk@1566 78cadc50-ecff-11dd-a971-7dbc132099af