Fix batch file 'goto' for previous labels

[kklobe]

Commit 7a4ee80 prevented the goto logic from finding a label earlier in the file. This commit just resets the file location to 0 at the beginning of the goto logic so it scans the entire file.

Test file (can't attach a .BAT):

@echo off
:start
echo "Hello"
goto DOIT
echo "Should not see this"
:DOIT
PAUSE
goto start

[kcgen]

My couple batch file examples here that launch games are still working ok.
Very nice exacting touch, kklobe !