dalvik/vm: Dalvik startup with a low memory footprint

Initialize concurrentStartBytes and createMspace using HEAP_MIN_FREE.
This helps save Android framework memory after boot.

This is for low memory targets only(~512MB RAM & hdpi resolution)
Also, set TARGET_ARCH_LOWMEM in the BoardConfig.mk file of a device
for this patch to take effect.

Change-Id: Ib164c5eaf3236fe2de2697e84de4ee85f8997e94
Revert "Zygote: Restrict slave mountspace so Dalvik apps can mount system-wide volumes"

No longer needed as su calls piped through the Superuser daemon run outside
zygote mountspaces.

This reverts commit a4c574321cfe9d874e69d365b1326ccc27f4e9dd.

Change-Id: I39ad8842604b5067dc3e735bcbe5fce1f3454ca8