Replace the uses of raw map()/unmap(), .etc calls with MemMap. Also
remove the direct use of MapPlatformData in the secondary allocator.
Also add setMemoryPermission() in MemMap.
Reviewed By: cryptoad
Differential Revision: https://reviews.llvm.org/D146454
Introduce a new data structure to manage the allocated pages from the
system. This is meant to deprecate certain memory system call wrappers
in Scudo, e.g., map()/unmap(). Besides, we would like to make
MapPlatformData to be appeared in platform specific data structure only.
Given that there are several allocators in Scudo and each of them has
different way of page management. The deprecation will be done in
several CLs. In this commit, we start from SizeClassAllocator64.
Reviewed By: cferris
Differential Revision: https://reviews.llvm.org/D146009
