added testcase for pattern matching on runtime variables

testsuite/compiler/check/strMatch/strMatchCnc.gf

@@ -0,0 +1,8 @@
+concrete strMatchCnc of strMatch = open Prelude in {
+  lincat S = {s : Str; b : Bool} ;
+  lin f x = case x.s of {
+              "" => {s="empty"; b=False} ;
+              _  => x
+            } ;
+  lin z = {s=""; b=False} ;
+}