GC triggering performance optimizations

Copy the correct starting heap size at process init.
Interfaces to set GC/managed heap parameters.

Change-Id: I0154d1523c3cfdb1214ed0315193cbb24704351f
GC: Improve the string parsing for GC parameter setting

Improve the string parsing for GC parameter system property.
Previously we only recoganize plain number for dalvik.vm.heapminfree
and dalvik.vm.heapconcurrentstart, while users tend to use format as
2m.  Improve the string parse to cover such cases.

Change-Id: Iaf0152bc4d77e1caabc307a9a7b0e5b261f8e441
Set some GC parameters only for dalvik

Commit https://github.com/CyanogenMod/android_frameworks_base/commit/8f566390bceee9f01b1721c4d00b1b246d26be16
fixed parsing of certain GC values. Before the result was "" and so the
if statement was always false, never executing the setTargetHeap* calls.

Now they are executed but ART currently doesn't support setting
heapminfree and heapconcurrentstart resulting in a UnsatisfiedLinkError
Exception.

Check for the used runtime first and only execute the methods for Dalvik.

Change-Id: I09e60802685acbec04598646e9f7700f33b53b4c
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>