Move UTF functions into namespace llvm.

Summary:
This lets people link against LLVM and their own version of the UTF
library.

I determined this only affects llvm, clang, lld, and lldb by running

$ git grep -wl 'UTF[0-9]\+\|\bConvertUTF\bisLegalUTF\|getNumBytesFor' | cut -f 1 -d '/' | sort | uniq
  clang
  lld
  lldb
  llvm

Tested with

  ninja lldb
  ninja check-clang check-llvm check-lld

(ninja check-lldb doesn't complete for me with or without this patch.)

Reviewers: rnk

Subscribers: klimek, beanz, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D24996

llvm-svn: 282822
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 43fa615..9bf3ae2 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3136,13 +3136,12 @@
   // Otherwise, convert the UTF8 literals into a string of shorts.
   IsUTF16 = true;
 
-  SmallVector<UTF16, 128> ToBuf(NumBytes + 1); // +1 for ending nulls.
-  const UTF8 *FromPtr = (const UTF8 *)String.data();
-  UTF16 *ToPtr = &ToBuf[0];
+  SmallVector<llvm::UTF16, 128> ToBuf(NumBytes + 1); // +1 for ending nulls.
+  const llvm::UTF8 *FromPtr = (const llvm::UTF8 *)String.data();
+  llvm::UTF16 *ToPtr = &ToBuf[0];
 
-  (void)ConvertUTF8toUTF16(&FromPtr, FromPtr + NumBytes,
-                           &ToPtr, ToPtr + NumBytes,
-                           strictConversion);
+  (void)llvm::ConvertUTF8toUTF16(&FromPtr, FromPtr + NumBytes, &ToPtr,
+                                 ToPtr + NumBytes, llvm::strictConversion);
 
   // ConvertUTF8toUTF16 returns the length in ToPtr.
   StringLength = ToPtr - &ToBuf[0];