Updates:
- Vector/ring/deque iterators now have ranged for-loop constructors (triggers a static assert on list & forward list)
- Added test code for ranged for-loop
- Deque iterators now have fast-case next/prev (i.e. stepping within a bucket)
- Iterator next/prev calls are all now inline in the headers
- Iterator list insert_after/insert_before implementation redelivered as std_push_before/std_push_after (for consistency)
- Iterator list entry erase reworked as std_pop_at (for consistency)
- gcc test build now uses -O3