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/global.c

@@ -12,7 +12,7 @@
 **
 ** This file contains definitions of global variables and constants.
 */
-#include "third_party/sqlite3/sqliteInt.h"
+#include "third_party/sqlite3/sqliteInt.inc"
 /* clang-format off */
 
 /* An array to map all upper-case characters into their corresponding
@@ -307,7 +307,7 @@ int sqlite3PendingByte = 0x40000000;
 u32 sqlite3SelectTrace = 0;
 u32 sqlite3WhereTrace = 0;
 
-#include "third_party/sqlite3/opcodes.h"
+#include "third_party/sqlite3/opcodes.inc"
 /*
 ** Properties of opcodes.  The OPFLG_INITIALIZER macro is
 ** created by mkopcodeh.awk during compilation.  Data is obtained