Add incremental blob support

[tenderlove]

BLOB-reading/writing can be done apart from SQL-Queries.

---

EXAMPLE:

..

filename = "test.png"

stmt = db.prepare("insert into files (filename, data) values (:filename,:data)")
stmt.bind_param("filename", filename)
stmt.bind_zeroblob("data", File.size(filename)
stmt.execute

f = File.new(filename, "w")

blob = db.blob_open('main','files','data',db.last_insert_row_id,1)
result = blob.write(f.read)

..

---

The space of the BLOB MUST be reserved. This can be done inside a SQL-query to:

"insert into files (filename, data) values ('test.png', zeroblob(2442))"

Moved from RubyForge