Allow lexer to handle string_view literals. Patch from Anton Bikineev.

This implements the compiler side of p0403r0. This patch was reviewed as
https://reviews.llvm.org/D26829.

llvm-svn: 290744
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 21bdd94..084bd4c 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -12913,7 +12913,7 @@
     //   Literal suffix identifiers that do not start with an underscore
     //   are reserved for future standardization.
     Diag(FnDecl->getLocation(), diag::warn_user_literal_reserved)
-      << NumericLiteralParser::isValidUDSuffix(getLangOpts(), LiteralName);
+      << StringLiteralParser::isValidUDSuffix(getLangOpts(), LiteralName);
   }
 
   return false;