Escape tokenize argument in enable_fts (#828)

The tokenize value passed to Table.enable_fts() was interpolated directly
into the CREATE VIRTUAL TABLE statement inside a single-quoted string
literal. A value containing a single quote could break out of that literal
and inject arbitrary SQL, which executes via executescript(). This is
reachable from the CLI via 'enable-fts --tokenize'.

Route the value through the existing Database.quote() helper so SQLite
itself escapes it. Legitimate tokenizers such as 'porter' are unaffected.
Adds a regression test.

sqlite_utils/db.py

@@ -3514,7 +3514,9 @@ class Table(Queryable):
                 table_fts=quote_identifier(self.name + "_fts"),
                 columns=", ".join(quote_identifier(c) for c in columns),
                 fts_version=fts_version,
-                tokenize=f"\n    tokenize='{tokenize}'," if tokenize else "",
+                tokenize=(
+                    f"\n    tokenize={self.db.quote(tokenize)}," if tokenize else ""
+                ),
             )
         )
         should_recreate = False