[PATCH] update configure.ac to follow new download location sqlite amalgamation

Hi,

seems like the sqlite developers have changed the naming conventions
for the sqlite amalgamation distribution package + stopped creating
the .tar.gz file.

The new address is now:
http://www.sqlite.org/sqlite-amalgamation-3071300.zip

instead of:
http://www.sqlite.org/sqlite-amalgamation-3.7.12.tar.gz

Attached patch updates configure to this new location. I can commit
this myself, but I'm wondering if I'm not overlooking something
obvious since this seems to be a strange move from the sqlite devs
side.

[[
Sqlite amalgamation distributions are now distributed as .zip and with a new
naming convention.

* configure.ac: update url of sqlite amalgamation file to its current location.
]]

Lieven