Bug 1011350 - Add mfbt support for PR_SET_VMA_ANON_NAME. r=njn r=froydnj

This is a Linux kernel feature present in newer Android and B2G devices
which allows attaching an arbitrary name to an anonymous memory regions,
thus tagging it for the purposes of procfs mapping lists and causing it
to be reported separately from adjacent regions with different names.
Bug 1011350 - Use TaggedAnonymousMemory to distinguish our various mmap call sites. r=njn

We can probably get more granular information than this, given that we
can re-tag memory after the initial mapping, or tag subregions of an
individual mmap() call differently.  But this is a start.
Bug 1011350 - Collect TaggedAnonymousMemory info in SystemMemoryReporter. r=njn

To allow flexibility in tagging, and integrate with non-Gecko uses of
this facility (e.g., Bionic's malloc() tags with "libc_malloc"), the
fixed list of memory kinds used to aggregate across processes is replaced
with arbitrary strings.
Bug 1026828 - Restore MOZ_STORAGE_MEMORY for system jemalloc after bug 938730. r=glandium