[SPARK-7314] [SPARK-3524] [PYSPARK] upgrade Pyrolite to 4.4

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

(cherry picked from commit e9b16e6)
Signed-off-by: Xiangrui Meng <meng@databricks.com>

core/pom.xml

@@ -362,7 +362,7 @@
     <dependency>
       <groupId>org.spark-project</groupId>
       <artifactId>pyrolite</artifactId>
-      <version>2.0.1</version>
+      <version>4.4</version>
     </dependency>
     <dependency>
       <groupId>net.sf.py4j</groupId>

core/src/main/scala/org/apache/spark/api/python/SerDeUtil.scala

@@ -56,16 +56,13 @@ private[spark] object SerDeUtil extends Logging {
     //    {'\0', 0, 0, 0} /* Sentinel */
     //  };
     // TODO: support Py_UNICODE with 2 bytes
-    // FIXME: unpickle array of float is wrong in Pyrolite, so we reverse the
-    // machine code for float/double here to workaround it.
-    // we should fix this after Pyrolite fix them
     val machineCodes: Map[Char, Int] = if (ByteOrder.nativeOrder().equals(ByteOrder.BIG_ENDIAN)) {
       Map('c' -> 1, 'B' -> 0, 'b' -> 1, 'H' -> 3, 'h' -> 5, 'I' -> 7, 'i' -> 9,
-        'L' -> 11, 'l' -> 13, 'f' -> 14, 'd' -> 16, 'u' -> 21
+        'L' -> 11, 'l' -> 13, 'f' -> 15, 'd' -> 17, 'u' -> 21
       )
     } else {
       Map('c' -> 1, 'B' -> 0, 'b' -> 1, 'H' -> 2, 'h' -> 4, 'I' -> 6, 'i' -> 8,
-        'L' -> 10, 'l' -> 12, 'f' -> 15, 'd' -> 17, 'u' -> 20
+        'L' -> 10, 'l' -> 12, 'f' -> 14, 'd' -> 16, 'u' -> 20
       )
     }
     override def construct(args: Array[Object]): Object = {