Merge the performance enhancements of trunk (and some obscure bug fixes)

into the sessions branch.

FossilOrigin-Name: 7f51ad97f0b24c57453d58faf25eee68861faa23

src/tclsqlite.c

@@ -3930,6 +3930,7 @@ int TCLSH_MAIN(int argc, char **argv){
   sqlite3_shutdown();
 
   Tcl_FindExecutable(argv[0]);
+  Tcl_SetSystemEncoding(NULL, "utf-8");
   interp = Tcl_CreateInterp();
 
 #if TCLSH==2