WL#5691: Add Per-Statement Link Targets

In some cases, multiple SQL statements (or variations that act as different
statements from the user point of view) are documented in the same section of
the Manual.

For example, the "flush" section includes the following variants (formatted as
s)

FLUSH DES_KEY_FILE
FLUSH HOSTS
FLUSH LOGS
FLUSH MASTER
FLUSH PRIVILEGES
FLUSH QUERY CACHE
FLUSH SLAVE
FLUSH STATUS
FLUSH TABLES [WITH READ LOCK]
FLUSH USER_RESOURCES

Under the current auto-linking setup, all of these link to the FLUSH page.

It would be a significant improvement if each of these autolinked directly to
the proper variant.

Step 1: Determine where we have multiple statements documented within a single
section.

FLUSH [...] is already mentioned in the description.

Another candidate would be START TRANSACTION / BEGIN [WORK] / COMMIT / ROLLBACK.

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