Bug 1105069 - Part 19: Remove JS_DumpHeap; r=jonco

--HG--
extra : rebase_source : a8ec7eee96d4e9937490bf9c9cdbd5e32cc7c993
Bug 1105069 - Part 20: Standardize GC structure accessors; r=jonco

--HG--
extra : rebase_source : 109967b39544ef7afcdee1c2fe443d8ffcf85736
Bug 1105069 - Part 21: Remove AsCell in preference of GCCellPtr; r=jonco, r=mccr8

--HG--
extra : rebase_source : 5c4470f3efbd9dbe3caee08ed88b07da549912e0