Move compiler flags into mkfiles.pl
Additional recommended security flags
warnings
GH-72: Don't show the username on the dialog

This causes startup hangs for some users.

I've been unable to determine a way to ask Windows for
a reasonable guess of the username that is not going to
go to the network.
pageant: save/reload keys at add/startup
pageant: setting for key persistence

This can only be enabled when no keys are loaded.  This sucks a bit,
but it doesn't have the paths of the keys available so it can't do it
directly.  Really should make the paths available.