Add test for MEMAVAIL and MAXAVAIL

Test heap functions

Author: boriel

tests/runtime/cases/maxavail.bas

@@ -0,0 +1,34 @@
+#include "lib/tst_framework.bas"
+
+INIT("Testing MEMAVAIL, MAXAVAIL")
+
+#include <alloc.bas>
+DIM hasError as Ubyte = 0
+
+SUB showResult()
+  PRINT TAB 12;
+  IF hasError THEN
+    hasError = 0
+    SHOW_ERROR
+  ELSE
+    SHOW_OK
+  END IF
+  PRINT
+END SUB
+
+
+PRINT maxavail(); " "; memavail();
+LET hasError = maxavail() <> 4764 or memavail() <> 4764
+showResult()
+
+a$ = "HELLO WORLD"
+PRINT maxavail(); " "; memavail();
+LET hasError = maxavail() <> 4749 or memavail() <> 4749
+showResult()
+
+a$ = a$ + a$
+PRINT maxavail(); " "; memavail();
+LET hasError = maxavail() <> 4723 or memavail() <> 4738
+showResult()
+
+FINISH