Initial pass on SQLite C ABI

This adds initial SQLite C ABI compatibility to Limbo to make sure we
drive the Rust API in the right way that allows us to implement SQLite
semantics.

sqlite3/examples/example.c

@@ -0,0 +1,30 @@
+#include "sqlite3.h"
+
+#include <stddef.h>
+#include <assert.h>
+#include <stdio.h>
+
+int main(int argc, char *argv[])
+{
+	sqlite3 *db;
+	int rc;
+
+	rc = sqlite3_open("local.db", &db);
+	assert(rc == SQLITE_OK);
+
+	sqlite3_stmt *stmt;
+
+	rc = sqlite3_prepare_v2(db, "SELECT 'hello, world' AS message", -1, &stmt, NULL);
+	assert(rc == SQLITE_OK);
+
+	rc = sqlite3_step(stmt);
+	assert(rc == SQLITE_OK);
+
+	const unsigned char *result = sqlite3_column_text(stmt, 0);
+
+	printf("result = %s\n", result);
+
+	sqlite3_close(db);
+
+	return 0;
+}