[add 'block' built in region
John Meacham <john@repetae.net>**20070522035432] hunk ./Grin/Val.hs 19
-region_heap = Item (toAtom "heap") TyRegion
+-- This allocates data on the heap.
+region_heap  = Item (toAtom "heap") TyRegion
+-- This allocates data in the innermost enclosing region, including implicit regions.
+region_block = Item (toAtom "block") TyRegion