merge revisions: 13909,13923,13924,13934,13935,13942,13943,13944,13946,13948,13950,13951,13952,13983,13994:
rtl: add enumerators to the basic classes
tests: add enumerators test which compiles and work both by fpc and dcc
compiler: 
  + start for-in loop implementation: implement for-in loop for types (enumerations and ranges), strings, arrays and sets. todo: perform type checking, optimize array and string loops - use temp for expression, implement for-in loop for classes
test:
  + add a simple test for the 'for-in' loop
compiler: fix string for-in loop. now it uses a temp variable to store string expression result
complier: fix for-in array loop. use a temp variable for the loop expression only if loop is not an open array loop
complier: continue enumerator implementation:
  + add operator enumerator which give an ability to add enumerator for an existent type (for example to override builtin string enumerator)
  + add class enumerator support via delphi compatible GetEnumerator method + enumerator class...