Added Atari Lynx versions of three sample programs.

The Lynx target can't build the usual versions because its library doesn't have conio output and stdio.

samples/lynx/hello.c

@@ -0,0 +1,43 @@
+/* Atari Lynx version of samples/hello.c, using TGI instead of conio */
+
+#include <tgi.h>
+
+
+/*****************************************************************************/
+/*                                   Data                                    */
+/*****************************************************************************/
+
+static const char Text[] = "Hello world!";
+
+
+/*****************************************************************************/
+/*                                   Code                                    */
+/*****************************************************************************/
+
+void main (void)
+{
+    unsigned int XMax, YMax;
+
+    tgi_install (tgi_static_stddrv);
+    tgi_init ();
+
+    /* Set screen color. */
+    tgi_setcolor (TGI_COLOR_WHITE);
+
+    /* Clear the screen. */
+    tgi_clear();
+
+    /* Ask for the screen size. */
+    XMax = tgi_getmaxx ();
+    YMax = tgi_getmaxy ();
+
+    /* Draw a frame around the screen. */
+    tgi_line (0, 0, XMax, 0);
+    tgi_lineto (XMax, YMax);
+    tgi_lineto (0, YMax);
+    tgi_lineto (0, 0);
+
+    /* Write the greeting in the middle of the screen. */
+    tgi_outtextxy ((tgi_getxres () - tgi_gettextwidth (Text)) / 2,
+                   (tgi_getyres () - tgi_gettextheight (Text)) / 2, Text);
+}