Properly track l-paren of a CXXFucntionalCastExpr.

In addition to storing more useful information in the AST, this
fixes a semantic check in template instantiation which checks whether
the l-paren location is valid.

Fixes PR16903.

llvm-svn: 188495

clang/lib/Analysis/ReachableCode.cpp

@@ -227,7 +227,7 @@ static SourceLocation GetUnreachableLoc(const Stmt *S,
     case Expr::CXXFunctionalCastExprClass: {
       const CXXFunctionalCastExpr *CE = cast <CXXFunctionalCastExpr>(S);
       R1 = CE->getSubExpr()->getSourceRange();
-      return CE->getTypeBeginLoc();
+      return CE->getLocStart();
     }
     case Stmt::CXXTryStmtClass: {
       return cast<CXXTryStmt>(S)->getHandler(0)->getCatchLoc();