Organize files into a low-level package.

This is in anticipation of the creation of a higher level interface.

Create a CL-CHARMS/LOW-LEVEL package for raw bindings.
Add barebones high-level interface files.
Initial high-level interface functions.

* WINDOW class, and some basic WINDOW construction/query functions

* Basic cursor functions

* Notion of the "standard window"
Add position querying, get-char, and write-char-at-* functions.
Add initialization functions to enable/disable non-blocking mode.
More properly handle INITIALIZE and FINALIZE.

Additionally, more sanity checking in some initialization functions.
Remove obsolete +STANDARD-WINDOW+.
Complete doctoring for INITIALIZE and WITH-CURSES.
Add clearing/repainting functions.
Add WRITE-STRING-AT-{POINT,CURSOR}.

Add CHECK-STATUS calls to output functions.
Add miscellaneous functions BEEP-CONSOLE and FLASH-CONSOLE.
Add CURSES-VERSION.