[SPARK-13157][SQL] Support any kind of input for SQL commands.

[hvanhovell]

The SparkSqlLexer currently swallows characters which have not been defined in the grammar. This causes problems with SQL commands, such as: add jar file:///tmp/a@b/TestUDTF.jar. In this example the @ is swallowed.

This PR adds an extra Lexer rule to handle such input, and makes a tiny modification to the ASTNode.

cc @davies @liancheng

[davies]

LGTM

[liancheng]

Maybe also add test cases where the remainder part contains whitespace characters?

[liancheng]

This PR probably also fixes SPARK-13150, which is about flaky tests caused by the @ removal bug.

[SparkQA]

Test build #50664 has finished for PR 11052 at commit 5a275ec.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #50665 has finished for PR 11052 at commit 3b1e475.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #2510 has finished for PR 11052 at commit c08a842.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[davies]

Merging this into master, thanks!