New arena memory allocator.

Before we were creating arenas for each method. The issue with doing this
is that we needed to memset each memory allocation. This can be improved
if you start out with arenas that contain all zeroed memory and recycle
them for each method. When you give memory back to the arena pool you do
a single memset to zero out all of the memory that you used.

Always inlined the fast path of the allocation code.

Removed the "zero" parameter since the new arena allocator always returns
zeroed memory.

Host dex2oat time on target oat apks (2 samples each).
real	1m11.958s
user	4m34.020s
sys	1m28.570s

real	1m9.690s
user	4m17.670s
sys	1m23.960s

Target device dex2oat samples (Mako, Thinkfree.apk):
Without new arena allocator:
0m26.47s real     0m54.60s user     0m25.85s system
0m25.91s real     0m54.39s user     0m26.69s system
0m26.61s real     0m53.77s user     0m27.35s system
0m26.33s real     0m54.90s user     0m25.30s system
0m26.34s real     0m53.94s user     0m27.23s system

With new arena allocator:
0m25.02s real     0m54.46s user     0m19.94s system
0m25.17s real     0m55.06s user     0m20.72s system
0m24.85s real     0m55.14s user     0m19.30s system
0m24.59s real     0m54.02s user     0m20.07s system
0m25.06s real     0m55.00s user     0m20.42s system

Correctness of Thinkfree.apk.oat verified by diffing both of the oat files.

Change-Id: I5ff7b85ffe86c57d3434294ca7a621a695bf57a9
25 files changed