Support EOF as statement separator in SQL scripts

Prior to Spring Framework 4.0.3, it was possible to supply a bogus
statement separator (i.e., a separator string that does not exist in
the configured SQL scripts) to ResourceDatabasePopulator with the side
effect that the entire contents of a script file would be interpreted
as a single SQL statement.

This undocumented feature was never intentional; however, some
developers came to rely on it. Unfortunately, changes made in
conjunction with SPR-9531 and SPR-11560 caused such scenarios to no
longer work.

This commit introduces first-class support for executing scripts which
contain a single statement that spans multiple lines but is not
followed by an explicit statement separator.

Specifically, ScriptUtils.EOF_STATEMENT_SEPARATOR may now be specified
as a 'virtual' statement separator to denote that a script contains a
single statement and no actual separator.

Issue: SPR-11687

spring-jdbc/src/test/resources/org/springframework/jdbc/datasource/init/drop-users-schema.sql

@@ -0,0 +1 @@
+DROP TABLE users IF EXISTS

spring-jdbc/src/test/resources/org/springframework/jdbc/datasource/init/users-data-without-separator.sql

@@ -0,0 +1,3 @@
+INSERT INTO
+users(first_name, last_name)
+values('Sam', 'Brannen')

spring-jdbc/src/test/resources/org/springframework/jdbc/datasource/init/users-schema-without-separator.sql

@@ -0,0 +1,5 @@
+CREATE TABLE users (
+	id INTEGER NOT NULL IDENTITY,
+	first_name VARCHAR(50) NOT NULL,
+	last_name VARCHAR(50) NOT NULL
+)