Merge changes I636784f7,I6bbc2e31,Ia9d986d1,I4e8178ce

* changes:
  Parse fstab.goldfish file from ramdisk.img
  androidPartitionType_fromString(): new function.
  android/filesystems/fstab_parser.h: New file.
  android/filesystems/ramdisk_extractor.h: new file.