Add dir-struct and skeleton code to files.

Add:
	src/
		-dir for all source files

	xterm/
		-add xterm source and header files: keyboard.* and
		xterm_control.*.

	makefile
		-add fairly robust makefile; not yet tested, though.

Mod:
	README.md
		-add content

	.gitignore
		-add build/ dir

	src/termcrate.c
		-add necessary skeleton code

	src/termcrate.h
		-add necessary struct/function declarations.

Ref:
	termcrate.c, termcrate.h
		-move termcrate.* to src