These interfaces are convoluted, rely on memory layout details that should not be exposed, and are often misued as proxies for other things (e.g., calling sbrk(0) repeatidly to determing heap use.) They are not part of any standard. While we must continue to support them for backwards compatability, most uses can be removed in a straightfoward manner.
Declare the undocumented break(2) system call COMPAT14 and remove public decleration and linkage defintion of it, sbrk, and brk interfaces. A later commit will introduce a libsbrk to allow their use for programs that can not be altered to avoid them (due to the way that tools like autoconf work, the symbol must not be directly linkable to avoid it being found and used even without a decleration).