[libami] add button, textbox and textinput from requestchoice/executecmd

Marcus had written up workbench style widgets inside the two external
helper programs requestchoice and executecmd.  This ports the code over
to libami.

Note that there isn't a generic gadget or collection of gadgets yet -
this is purely a refactor of the code, and the upcoming commit that
migrates requestchoice/executecmd over to use them just handles them
directly via xlib like they have always done.

libami/gadget_textinput.h

@@ -0,0 +1,46 @@
+#ifndef	__LIBAMI__GADGET_TEXTINPUT_H__
+#define	__LIBAMI__GADGET_TEXTINPUT_H__
+
+struct gadget_textinput {
+	Display *dpy;
+	struct DrawInfo *dri;
+	Window w;
+	GC gc;
+#ifdef USE_FONTSETS
+	XIC xic;
+#endif
+	int x;
+	int y;
+	int width;
+	int height;
+
+	/* XXX TODO: create a string representation here already */
+	char *buf;
+	int len;
+	int size;
+
+	/* Position of textbox cursor and rendering start */
+	int cur_pos;
+	int left_pos;
+	int cur_x;
+
+	int selected;
+	int crlf;
+};
+
+extern	struct gadget_textinput * gadget_textinput_create(Display *dpy,
+	    struct DrawInfo *dri, GC gc, Window mainwin,
+	    int x, int y, int width, int height, int text_size);
+#ifdef USE_FONTSETS
+extern	void gadget_textinput_set_xic(struct gadget_textinput *g, XIC xic);
+#endif
+extern	void gadget_textinput_repaint(struct gadget_textinput *b);
+extern	void gadget_textinput_free(struct gadget_textinput *b);
+extern	void gadget_textinput_keyevent(struct gadget_textinput *b,
+	    XKeyEvent *e);
+extern	void gadget_textinput_buttonevent(struct gadget_textinput *b,
+	    XButtonEvent *e);
+extern	void gadget_textinput_selected(struct gadget_textinput *b, int selected);
+extern	int gadget_textinput_crlf(struct gadget_textinput *b);
+
+#endif	/* __LIBAMI__GADGET_TEXTINPUT_H__ */