Use libc++ on FreeBSD as on Darwin

This could use some refinement still, but the previous behaviour of adding
-stdlib=libstc++ on FreeBSD w/ Clang is the least likely case to work.

llvm.org/pr17910


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@200646 91177308-0d34-0410-b5e6-96231b3b80d8
Update header comment to match filename



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@200647 91177308-0d34-0410-b5e6-96231b3b80d8
Remove failure decorators for FreeBSD bug

The issue described in llvm.org/pr18065 is actually due to FreeBSD bug
theads/186309 [1], which is now fixed in FreeBSD SVN r261354 [2] and will
be merged to release branches shortly.

Diagnosed and fixed by John Wolfe.

[1] http://www.freebsd.org/cgi/query-pr.cgi?pr=186309
[2] http://svnweb.freebsd.org/base?view=revision&revision=261354


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@200648 91177308-0d34-0410-b5e6-96231b3b80d8