Merged r16205, r16220, r16237, r16249, r16262, r16269, r16273 into 3.20 branch.

Mark HStringCompareAndBranch as potentially causing GCs.

Prevent empty handle dereference in Runtime_InternalNumberFormat.

Fix null handle deref in InternalDateFormat

Fix a bug in Div when all uses are truncating

Fix "Hole" leak in TryBuildConsolidatedElementLoad

Never clear debug-stub call ICs. Make a clear distinction between is_debug_stub used everywhere but the debugger, and IsDebugBreak, used by the debugger.

Fix deoptimization bug, where recursive call can frighten and confuse the unwitting, simple, poor caveman that is Runtime_NotifyDeoptimized.

BUG=chromium:274438,chromium:275467,274164
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/23761002

git-svn-id: https://v8.googlecode.com/svn/branches/3.20@16426 ce2b1a6d-e550-0410-aec6-3dcde31c8c00