Add another testcase for swig#1384

A string in parentheses could be treated as an integer (depending on
the state the stack was left in by previously evaluated expressions).

Author: ojwb

Examples/test-suite/errors/pp_expressions_bad.i

@@ -41,3 +41,13 @@
 #if(1)
 #warning Warning okay: #if(1)
 #endif
+
+/* The SWIG preprocessor support strings with equality/inequality tests.
+ * Check error cases.
+ */
+#if "TWO" == 1
+#endif
+
+/* This didn't fail prior with SWIG < 4.1.  Github #1384. */
+#if 1 == ("TWO")
+#endif

Examples/test-suite/errors/pp_expressions_bad.stderr

@@ -17,3 +17,7 @@ pp_expressions_bad.i:30: Error: Extraneous #endif.
 pp_expressions_bad.i:32: Error: Unknown SWIG preprocessor directive: if456e (if this is a block of target language code, delimit it with %{ and %})
 pp_expressions_bad.i:33: Error: Extraneous #endif.
 pp_expressions_bad.i:42: Warning 204: CPP #warning, "Warning okay: #if(1)".
+pp_expressions_bad.i:48: Warning 202: Could not evaluate expression '"TWO" == 1'
+pp_expressions_bad.i:48: Warning 202: Error: 'Can't mix strings and integers in expression'
+pp_expressions_bad.i:52: Warning 202: Could not evaluate expression '1 == ("TWO")'
+pp_expressions_bad.i:52: Warning 202: Error: 'Can't mix strings and integers in expression'