Don't use libc's "char *basename(char *)" or "char *dirname(char *)" as they are not thread safe.

I switched the lldb_private::FileSpec code over to use "llvm::StringRef llvm::sys::path::filename(llvm::StringRef)" for basename() and "llvm::StringRef llvm::sys::path::parent_path(llvm::StringRef)" for dirname().

<rdar://problem/16870083>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@209917 91177308-0d34-0410-b5e6-96231b3b80d8