Replace all uses of PathV1::isAbsolute with PathV2::is_{absolute,relative}.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@122087 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/HeaderSearch.cpp b/lib/Lex/HeaderSearch.cpp
index 6b74090..d11e87f 100644
--- a/lib/Lex/HeaderSearch.cpp
+++ b/lib/Lex/HeaderSearch.cpp
@@ -211,7 +211,7 @@
                                           const DirectoryLookup *&CurDir,
                                           const FileEntry *CurFileEnt) {
   // If 'Filename' is absolute, check to see if it exists and no searching.
-  if (llvm::sys::Path::isAbsolute(Filename.begin(), Filename.size())) {
+  if (llvm::sys::path::is_absolute(Filename)) {
     CurDir = 0;
 
     // If this was an #include_next "/absolute/file", fail.