ram_{free,total}: system fallback if other fails

Author: scivision

+stdlib/ram_free.m

@@ -24,7 +24,9 @@
   bytes = ram_free_java();
 elseif stdlib.has_python()
   bytes = py_ram_free();
-else
+end
+
+if bytes <= 0
   bytes = ram_free_system();
 end
 

+stdlib/ram_total.m

@@ -15,7 +15,9 @@
   bytes = System.GC.GetGCMemoryInfo().TotalAvailableMemoryBytes;
 elseif stdlib.has_java()
   bytes = ram_total_java();
-else
+end
+
+if bytes <= 0
   bytes = ram_total_system();
 end