fixes duplicate header installation http://llvm.org/bugs/show_bug.cgi?id=18681 Patch by Ryuta Suzuki <oroppas gmail com>
fixes duplicate header installation
http://llvm.org/bugs/show_bug.cgi?id=18681
Patch by Ryuta Suzuki <oroppas gmail com>

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@210577 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx