Simplify, Use only Left-Ctrl

A trick to co-exist Windows shortcut and Emacs:

1. Assign Only Left-Ctrl to Emacs key.
2. Remap Left-Alt to R-Ctrl
3. Keep R-Ctrl as-is

You can use LAlt+C as Windows Ctrl-C (Copy) etc,
This is somewhat similar to MacOSX keybind.

For my own purpose, I removed all ^X two-stroke key binds.