Another test for preprocessor corner cases

From-SVN: r31558

gcc/testsuite/gcc.dg/lineno.c

+/* { dg-do compile } */
+/* { dg-options "-Wwrite-strings" } */ 
+/* The purpose of this test is to ensure that line numbers in diagnostics
+   are accurate after macros whose arguments contain newlines and are
+   substituted multiple times.  The semicolons are on separate lines because
+   #line can only correct numbering on line boundaries.  */
+#define one(x) x
+#define two(x) x x
+#define four(x) two(x) two(x)
+
+int
+main(void)
+{
+  char *A;
+
+  A = "text";		/* { dg-warning "discards qualifiers" "case zero" } */
+  A = one("text"
+	  "text")
+	;		/* { dg-warning "discards qualifiers" "case one" } */
+  A = two("text"
+	  "text")
+	;		/* { dg-warning "discards qualifiers" "case two" } */
+  A = four("text"
+	   "text")
+	;		/* { dg-warning "discards qualifiers" "case four" } */
+
+  return 0;
+}