This fixes the problem where when building with gccgo, sqlite3.c is
overwritten, leading to a build failure.
An alternative would have been to move sqlite3*.{c,h} to a subdirectory,
but that seems to confuse the linker a fair bit and would just swap one
implementation-dependent issue for another.
Closes#20
Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>