Implement LWG 2936: Path comparison is defined in terms of the generic format

This patch implements path::compare according to the current spec. The
only observable change is the ordering of "/foo" and "foo", which orders
the two paths based on having or not having a root directory (instead
of lexically comparing "/" to "foo").

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@349881 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed