Remove test for eof from istreambuf_iterator constructors.  It is no longer necessary and potentially violates the constructor's noexcept spec.
Remove test for eof from istreambuf_iterator constructors.  It is no longer necessary and potentially violates the constructor's noexcept spec.

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@171232 91177308-0d34-0410-b5e6-96231b3b80d8

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