Add catches_strings test to test throws char * typemap

Examples/test-suite/mzscheme/catches_strings_runme.scm

@@ -0,0 +1,11 @@
+(load-extension "catches_strings.so")
+(require (lib "defmacro.ss"))
+
+(define exception_thrown "no exception thrown for kin")
+(with-handlers ([exn:fail? (lambda (exn)
+                             (set! exception_thrown (exn-message exn)))])
+  (StringsThrower-charstring))
+(unless (string-contains? exception_thrown "charstring message")
+  (error (format "incorrect exception message: ~a" exception_thrown)))
+
+(exit 0)