Rename sqlite3.{c,h} to sqlite3-binding.{c,h}

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>

_example/mod_vtable/sqlite3_mod_vtable.cc

@@ -1,6 +1,6 @@
 #include <string>
 #include <sstream>
-#include <sqlite3.h>
+#include <sqlite3-binding.h>
 #include <sqlite3ext.h>
 #include <curl/curl.h>
 #include "picojson.h"