Fix off-by-one error in StringLiteral::getLocationOfByte.

This fixes PR10223.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134183 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index fdcb77f..1d0319f 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -593,7 +593,7 @@
     
     // If the byte is in this token, return the location of the byte.
     if (ByteNo < TokNumBytes ||
-        (ByteNo == TokNumBytes && TokNo == getNumConcatenated())) {
+        (ByteNo == TokNumBytes && TokNo == getNumConcatenated() - 1)) {
       unsigned Offset = SLP.getOffsetOfStringByte(TheTok, ByteNo); 
       
       // Now that we know the offset of the token in the spelling, use the