The size and starting position of Urbit's reserved memory block is set by `U3_OS_LoomBits` and `U3_OS_LoomBase` in `include/c/portable.h`.
`U3_OS_LoomBase` is referenced in `include/noun/allocate.h` and sets the position in memory of u3_Loom. This is good.
However, `U3_OS_LoomBits` is not actually used to set the size of the reserved memory block. Instead:
in `include/allocate.h`,
- `u3a_bits` is defined
- `u3a_bits` → `u3a_bytes`
in `noun/manage.c`,
- `u3a_bytes` → `len_w` in `_cm_init()`
- `len_w` sets the reserved memory block size
This proposal puts `U3_OS_LoomBits` back to work by defining `u3a_bits` with it.
