Add an option to stop treating blank lines as a statement separator

[edeadington]

ST_SEMICOLON matches "\n\n\n", so three newlines in a row end a statement, the same as ;. No SQL dialect ends a statement at a blank line (the closest is SQL*Plus, which does so unless SQLBLANKLINES is on), but generated or hand-formatted SQL often has blank lines inside a single statement, and that SQL then fails to parse at whatever comes after the gap.

This has come up a few times (#1891, #1988, #2156, #2346, #2352). Those were closed because the behaviour is by design, so this PR leaves it alone. Instead it adds Feature.allowBlankLinesAsStatementSeparator, which is enabled by default. Callers who want blank lines treated as plain whitespace can turn it off with withBlankLinesAsSeparator(false):

CCJSqlParserUtil.parse(sql, parser -> parser.withBlankLinesAsSeparator(false));

The ST_SEMICOLON token is unchanged. When the option is off, SimpleCharStream.BeginToken() replaces the first newline of a \n\n\n run with a space before the token manager sees it, as allowHashLineComments already does. Unlike stripping blank lines before parsing, this leaves string literals alone and keeps error line numbers accurate. ;, go and / still separate statements.

SQL	Default (unchanged)	withBlankLinesAsSeparator(false)
SELECT a\n\n\nFROM t	Encountered: <K_FROM> at line 4	SELECT a FROM t
SELECT a FROM t\n\n\nWHERE b = 1	Encountered: <K_WHERE> at line 4	SELECT a FROM t WHERE b = 1
SELECT a FROM t WHERE b = 1\n\n\nAND c = 2	Encountered: <K_AND> at line 4	SELECT a FROM t WHERE b = 1 AND c = 2
SELECT a FROM t\n\n\nUNION\nSELECT b FROM u	Encountered: <K_UNION> at line 4	SELECT a FROM t UNION SELECT b FROM u
parseStatements("SELECT 1\n\n\nSELECT 2")	2 statements	Parse error, since this is one statement with no separator

testBlankLinesAsSeparatorDisabled covers blank lines in each clause, trailing blank lines, a string literal containing \n\n\n, the other separators, and the reported error position.

[manticore-projects]

Smart trick, appreciated!