This change adds AllocateMemory and DeallocateMemory methods to the SBProcess
API, so that clients can allocate and deallocate memory blocks within the
process being debugged (for storing JIT-compiled code or other uses).
(I am developing a debugger + REPL using the API; it will need to store
JIT-compiled code within the target.)
Reviewed By: clayborg, jingham
Differential Revision: https://reviews.llvm.org/D105389