@Override
    public long availableSize() {
        long v = mallinfo.fordblks;
        return v << 20; // Due to too few bits in ancient mallinfo vespamalloc reports in 1M units
    }
Gives access to the information provided by the C library mallinfo() function.

@author baldersheim
vespajlib/src/main/java/com/yahoo/nativec/MallInfo.java