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/where.c

@@ -16,8 +16,8 @@
 ** so is applicable.  Because this module is responsible for selecting
 ** indices, you might also think of this module as the "query optimizer".
 */
-#include "third_party/sqlite3/sqliteInt.h"
-#include "third_party/sqlite3/whereInt.h"
+#include "third_party/sqlite3/sqliteInt.inc"
+#include "third_party/sqlite3/whereInt.inc"
 /* clang-format off */
 
 /*