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/include/sqlite3.h

@@ -0,0 +1,44 @@
+#ifndef LIMBO_SQLITE3_H
+#define LIMBO_SQLITE3_H
+
+#include <stdint.h>
+
+#define SQLITE_OK 0
+
+#define SQLITE_ERROR 1
+
+#define SQLITE_BUSY 5
+
+#define SQLITE_NOTFOUND 14
+
+#define SQLITE_MISUSE 21
+
+#define SQLITE_ROW 100
+
+#define SQLITE_DONE 101
+
+typedef struct sqlite3 sqlite3;
+
+typedef struct sqlite3_stmt sqlite3_stmt;
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+int sqlite3_open(const char *filename, sqlite3 **db_out);
+
+int sqlite3_close(sqlite3 *db);
+
+int sqlite3_prepare_v2(sqlite3 *db, const char *sql, int len, sqlite3_stmt **out_stmt, const char **tail);
+
+int sqlite3_finalize(sqlite3_stmt *stmt);
+
+int sqlite3_step(sqlite3_stmt *db);
+
+const unsigned char *sqlite3_column_text(sqlite3_stmt *db, int idx);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus
+
+#endif /* LIMBO_SQLITE3_H */