Fix interaction between serialization and c++1z feature.
In c++1z, static_assert is not required to have a StringLiteral message, where
previously it was required. Update the AST Reader to be able to handle a
null StringLiteral.
llvm-svn: 281286
diff --git a/clang/test/Modules/Inputs/static_assert/module.modulemap b/clang/test/Modules/Inputs/static_assert/module.modulemap
new file mode 100644
index 0000000..bb00c84
--- /dev/null
+++ b/clang/test/Modules/Inputs/static_assert/module.modulemap
@@ -0,0 +1 @@
+module a { header "a.h" }