Add test case for hex floating point constants in < C99 mode

- For: rdar://6096838


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@54036 91177308-0d34-0410-b5e6-96231b3b80d8

test/Lexer/rdr-6096838.c

@@ -0,0 +1,14 @@
+/* RUN: clang -fsyntax-only -verify %s &&
+ * RUN: clang -std=gnu89 -fsyntax-only -verify %s &&
+ * RUN: clang -DPEDANTIC -pedantic -std=gnu89 -fsyntax-only -verify %s
+ */
+
+#ifdef PEDANTIC
+
+long double d = 0x0.0000003ffffffff00000p-16357L; /* expected-warning {{ hexadecimal floating constants are a C99 feature }} */
+
+#else
+
+long double d = 0x0.0000003ffffffff00000p-16357L;
+
+#endif