Fix PR41017 - Build failure with _LIBCPP_DEBUG=0 and non-const-ref
comparator for std::sort()

Our debug comparator assumed that the comparator it wraps would always
accepts the values by const ref. This isn't required by the standard.

This patch makes our __debug_less comparator forward the constness.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@355752 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed