In ledger-do-reconcile, don't act on windows when reconcile hasn't one

Ledger-do-reconcile might be called indirectly (in the after-save-hook
for example) and one might not want this buffer she has buried to show
up again when she is saving another (even related) buffer.
Ensure that the reconcile buffer is shown when ledger-reconcile is called.
Merge pull request #155 from vanicat/t/reconcile_and_windows

T/reconcile and windows