emitter: Reuse space within branches->patches.
emitter: Reuse space within branches->patches.

Previously, patch_pos wouldn't be set to what it originally was after the
patches were applied. So every patch that came through would use new space.
instead of possibly using old space.

This reduces sanity.ly by one alloc, but that's not a good metric since it
isn't steady.

jesserayadkins/lily,jesserayadkins/lily,jesserayadkins/lily,FascinatedBox/lily,FascinatedBox/lily,FascinatedBox/lily,FascinatedBox/lily