1. Update the IANA tz db to 2015b.
  - http://mm.icann.org/pipermail/tz-announce/2015-March/000029.html
  - Mongolia decided to observe DST again in 2015 starting on the last
    Sunday in March.
  - Palestine's DST start date is corrected to be March 28 instead of 27th.

2. Add a script to download the tz database files (update_tz.sh)

3. Check in scripts/make_n_copy_data.sh that I've been using to build ICU
   data/assembly files and update README.chromium.

4. Update android/patch_locale.sh to apply android/brkitr.patch as well.

BUG=473288
TEST=1. In JavaScript console, run the following.
  mar27_2015_1200 = new Date("03/27/2015 12:00Z")
  mar28_2015_1200 = new Date("03/28/2015 12:00Z")
  mar27_2015_1200.toLocaleString("en", {timeZone: "Asia/Gaza"}
  mar28_2015_1200.toLocaleString("en", {timeZone: "Asia/Gaza"}
  apr15_2014_1200 = new Date("04/15/2014 12:00Z")
  apr15_2015_1200 = new Date("04/15/2015 12:00Z")
  apr15_2014_1200.toLocaleString("en", {timeZone: "Asia/Ulan_Bator"}
  apr15_2015_1200.toLocaleString("en", {timeZone: "Asia/Ulan_Bator"}

In Asia/Gaza, Mar 27 12:00Z should be 2PM and mar28 12:00Z should be 3PM.
In Asia/Ulan_Bator, April 15 12:00Z should be 8PM in 2014 and should be 9PM
in 2015. Ulan_Bator does not work due to http://crbug.com/364374.

R=mark@chromium.org

Review URL: https://codereview.chromium.org/1051193002