Lift VFS from clang to llvm (NFC)

This patch moves the virtual file system form clang to llvm so it can be
used by more projects.

Concretely the patch:
 - Moves VirtualFileSystem.{h|cpp} from clang/Basic to llvm/Support.
 - Moves the corresponding unit test from clang to llvm.
 - Moves the vfs namespace from clang::vfs to llvm::vfs.
 - Formats the lines affected by this change, mostly this is the result of
   the added llvm namespace.

RFC on the mailing list:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/126657.html

Differential revision: https://reviews.llvm.org/D52783

llvm-svn: 344140

1 files changed, 3 insertions, 2 deletions

diff --git a/clang/lib/Lex/PPLexerChange.cpp b/clang/lib/Lex/PPLexerChange.cpp
index 2ec075fa348..76ccfb73fd5 100644
--- a/clang/lib/Lex/PPLexerChange.cpp
+++ b/clang/lib/Lex/PPLexerChange.cpp
@@ -304,9 +304,10 @@ void Preprocessor::diagnoseMissingHeaderInUmbrellaDir(const Module &Mod) {
 
   ModuleMap &ModMap = getHeaderSearchInfo().getModuleMap();
   const DirectoryEntry *Dir = Mod.getUmbrellaDir().Entry;
-  vfs::FileSystem &FS = *FileMgr.getVirtualFileSystem();
+  llvm::vfs::FileSystem &FS = *FileMgr.getVirtualFileSystem();
   std::error_code EC;
-  for (vfs::recursive_directory_iterator Entry(FS, Dir->getName(), EC), End;
+  for (llvm::vfs::recursive_directory_iterator Entry(FS, Dir->getName(), EC),
+       End;
        Entry != End && !EC; Entry.increment(EC)) {
     using llvm::StringSwitch;