Further polish SQLite vendoring

- Now integrated with `make tags` for Emacs IDE features
- Delete some old deprecated broken full-text search engines
- Rename .h → .inc files that don't meet our definition of header
- Make sure every #include line is normal form so tools understand

See #162

third_party/sqlite3/mem2.c

@@ -19,7 +19,7 @@
 ** This file contains implementations of the low-level memory allocation
 ** routines specified in the sqlite3_mem_methods object.
 */
-#include "third_party/sqlite3/sqliteInt.h"
+#include "third_party/sqlite3/sqliteInt.inc"
 /* clang-format off */
 
 /*