Fixes running 'hg serve' with Windows executable and no explicit template path configured. PY2EXE executables don't support __file__ but do place the directory of the shared code library into sys.prefix. Fixes bug 152.

#!/bin/sh
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "0 0"
ls
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "0 0"
hg co 0
# B should disappear
ls