[SQL] Using safe floating-point numbers in doctest

Test code in `sql.py` tries to compare two floating-point numbers directly, and cased [build failure(s)](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/18365/consoleFull).

[Doctest documentation](https://docs.python.org/3/library/doctest.html#warnings) recommends using numbers in the form of `I/2**J` to avoid the precision issue.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #1925 from liancheng/fix-pysql-fp-test and squashes the following commits:

0fbf584 [Cheng Lian] Removed unnecessary `...' from inferSchema doctest
e8059d4 [Cheng Lian] Using safe floating-point numbers in doctest

(cherry picked from commit b4a05928e95c0f6973fd21e60ff9c108f226e38c)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2677] BasicBlockFetchIterator#next can wait forever

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #1632 from sarutak/SPARK-2677 and squashes the following commits:

cddbc7b [Kousuke Saruta] Removed Exception throwing when ConnectionManager#handleMessage receives ack for non-referenced message
d3bd2a8 [Kousuke Saruta] Modified configuration.md for spark.core.connection.ack.timeout
e85f88b [Kousuke Saruta] Removed useless synchronized blocks
7ed48be [Kousuke Saruta] Modified ConnectionManager to use ackTimeoutMonitor ConnectionManager-wide
9b620a6 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-2677
0dd9ad3 [Kousuke Saruta] Modified typo in ConnectionManagerSuite.scala
7cbb8ca [Kousuke Saruta] Modified to match with scalastyle
8a73974 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-2677
ade279a [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-2677
0174d6a [Kousuke Saruta] Modified ConnectionManager.scala to handle the case remote Executor cannot ack
a454239 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-2677
9b7b7c1 [Kousuke Saruta] (WIP) Modifying ConnectionManager.scala

(cherry picked from commit 76fa0eaf515fd6771cdd69422b1259485debcae5)
Signed-off-by: Josh Rosen <joshrosen@apache.org>
[SPARK-3048][MLLIB] add LabeledPoint.parse and remove loadStreamingLabeledPoints

Move `parse()` from `LabeledPointParser` to `LabeledPoint` and make it public. This breaks binary compatibility only when a user uses synthesized methods like `tupled` and `curried`, which is rare.

`LabeledPoint.parse` is more consistent with `Vectors.parse`, which is why `LabeledPointParser` is not preferred.

freeman-lab tdas

Author: Xiangrui Meng <meng@databricks.com>

Closes #1952 from mengxr/labelparser and squashes the following commits:

c818fb2 [Xiangrui Meng] merge master
ce20e6f [Xiangrui Meng] update mima excludes
b386b8d [Xiangrui Meng] fix tests
2436b3d [Xiangrui Meng] add parse() to LabeledPoint

(cherry picked from commit 7e70708a99949549adde00cb6246a9582bbc4929)
Signed-off-by: Xiangrui Meng <meng@databricks.com>
[SPARK-3081][MLLIB] rename RandomRDDGenerators to RandomRDDs

`RandomRDDGenerators` means factory for `RandomRDDGenerator`. However, its methods return RDDs but not RDDGenerators. So a more proper (and shorter) name would be `RandomRDDs`.

dorx brkyvz

Author: Xiangrui Meng <meng@databricks.com>

Closes #1979 from mengxr/randomrdds and squashes the following commits:

b161a2d [Xiangrui Meng] rename RandomRDDGenerators to RandomRDDs

(cherry picked from commit ac6411c6e75906997c78de23dfdbc8d225b87cfd)
Signed-off-by: Xiangrui Meng <meng@databricks.com>