Use JEMALLOC_INLINE_C everywhere it's appropriate.
Fix prof_{enter,leave}() calls to pass tdata_self.
mark huge allocations as unlikely

This cleans up the fast path a bit more by moving away more code.
avoid redundant chunk header reads

* use sized deallocation in iralloct_realign
* iralloc and ixalloc always need the old size, so pass it in from the
  caller where it's often already calculated