Increase the android VM heap size.

开机初始化会在对应的init.rc中增加如下一行：setprop dalvik.vm.heapsize 48m。

ActivityManager.java (android/frameworks/base/core/java/android/app):  String vmHeapSize = SystemProperties.get("dalvik.vm.heapsize", "16m");
AndroidRuntime.cpp (android/frameworks/base/core/jni):    property_get("dalvik.vm.heapsize", heapsizeOptsBuf+4, "16m");
Init.pxa910-based.rc (android/vendor/omap/tw50f/rootdir): setprop dalvik.vm.heapsize 32m
Init.pxa910-based.rc (android/vendor/omap/tw60f/rootdir): setprop dalvik.vm.heapsize 32m
Main.c (android/external/qemu/android):                   boot_property_add("dalvik.vm.heapsize",tmp);