M PyShell.py

M PyShell.py
M idle
M setup.py

To be able to run from the source directory or from an installed version
of IDLE, and also to allow the subprocess to find run(), Python needs to
have the idlelib package on its path.

1. Modify setup.py to supply a .pth file living at same level as idlelib
2. Move boolcheck to PyShell.py
3. Remove boolcheck and path setting code from the "idle" script