[RFC PATCH 07/11] malloc: make arena size configurable on startup

[DJ Delorie]

I have no fundamental problem with tuning the heap size, but...

1. The heap size must always be a power of two; you need to enforce that
   in the tunable callback.

2. Do you have any benchmarks that show that these changes don't affect
   performance?  I don't mean differing size heaps, I mean changing a
   constant to a variable in the code.

3. I don't see the point of heap_max_specified.