Now collections accept plain struct

Also fixed impl prefixes and function modifiers
Added new test for all possible data types
Fixed some READMEs

examples/hashmap/README.md

@@ -1,4 +1,5 @@
 # Hashmap examples
 
 * countries - Uses a hashmap to map the country name to its population
+* foreach.c - ForEach macro example
 * iterator.c - A complete example of the hashmap iterator