This PR upgrades Pyrolite to 4.4, which contains the bug fix for SPARK-3524 and some other performance improvements (e.g., SPARK-6288). The artifact is still under `org.spark-project` on Maven Central since there is no official release published there.

Author: Xiangrui Meng <meng@databricks.com>

Closes #5850 from mengxr/SPARK-7314 and squashes the following commits:

2ed4a95 [Xiangrui Meng] Merge remote-tracking branch 'apache/master' into SPARK-7314
da3c2dd [Xiangrui Meng] remove my repo
fe7e29b [Xiangrui Meng] switch to maven central
6ddac0e [Xiangrui Meng] reverse the machine code for float/double
d2d5b5b [Xiangrui Meng] change back to 4.4
7824a9c [Xiangrui Meng] use Pyrolite 3.1
cc3903a [Xiangrui Meng] upgrade Pyrolite to 4.4-0 for testing