Increase bundled SQLite variables and depth

[pimeys]

We've been hitting the default MAX_VARIABLE_NUMBER and
MAX_EXPR_DEPTH with quite basic tests here in Prisma. I was able to
run the tests by using the Arch Linux packaged libsqlite3, but when
turning on the bundled version I was able to get my test to crash with
this test project:

https://github.com/pimeys/sqlite_parameter_test

Now taking a look how Arch Linux builds sqlite, I was able to find two
flags fixing the issue:

https://git.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/sqlite#n35

I think it would be safe to include them in rusqlite.

[gwenn]

Expected (or something like that):

diff --git a/libsqlite3-sys/build.rs b/libsqlite3-sys/build.rs
index e6942d0..66c6b8d 100644
--- a/libsqlite3-sys/build.rs
+++ b/libsqlite3-sys/build.rs
@@ -79,6 +79,9 @@ mod build_bundled {
         if cfg!(feature = "session") {
             cfg.flag("-DSQLITE_ENABLE_SESSION");
         }
+        if Some(limit) = env::var("SQLITE_MAX_VARIABLE_NUMBER") {
+            cfg.flag("-DSQLITE_MAX_VARIABLE_NUMBER="+limit);
+        }
         cfg.compile("libsqlite3.a");

         println!("cargo:lib_dir={}", out_dir);

[pimeys]

Updated the pull request.

[gwenn]

Sorry,
I forgot:

        if Some(limit) = env::var("SQLITE_MAX_VARIABLE_NUMBER") {
            cfg.flag("-DSQLITE_MAX_VARIABLE_NUMBER="+limit);
        } 
        println!("cargo:rerun-if-env-changed=SQLITE_MAX_VARIABLE_NUMBER");

Thanks.

[pimeys]

Done.

[gwenn]

Perfect.